Co-authored-by: Bastian Köcher <git@kchr.de>

Co-authored-by: Bastian Köcher <git@kchr.de>

Update from bkontur running command 'bench --pallet polkadot_runtime_parachains::paras --runtime westend rococo'

Returning an iterator in `TracksInfo::tracks()` instead of a static
slice allows for more flexible implementations of `TracksInfo` that can
use the chain storage without compromising a lot on the
performance/memory penalty if we were to return an owned `Vec` instead.

---------

Co-authored-by: Pablo Andrés Dorado Suárez <hola@pablodorado.com>

Closes #4315

---------

Co-authored-by: Guillaume Thiolliere <guillaume.thiolliere@parity.io>

# Utility Call Fallback

This introduces a new extrinsic: **`if_else`**

Which first attempts to dispatch the `main` call(s). If the `main`
call(s) fail, the `fallback` call(s) is dispatched instead. Both calls
are executed with the same origin.

In the event of a fallback failure the whole call fails with the weights
returned.

## Use Case
Some use cases might involve submitting a `batch` type call in either
main, fallback or both.

Resolves #6000

Polkadot Address: 1HbdqutFR8M535LpbLFT41w3j7v9ptEYGEJKmc6PKpqthZ8

---------

Co-authored-by: rainbow-promise <154476501+rainbow-promise@users.noreply.github.com>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

## Multi Block Election Pallet

This PR adds the first iteration of the multi-block staking pallet. 

From this point onwards, the staking and its election provider pallets
are being customized to work in AssetHub. While usage in solo-chains is
still possible, it is not longer the main focus of this pallet. For a
safer usage, please fork and user an older version of this pallet.

---

## Replaces

- [x] https://github.com/paritytech/polkadot-sdk/pull/6034 
- [x] https://github.com/paritytech/polkadot-sdk/pull/5272

## Related PRs: 

- [x] https://github.com/paritytech/polkadot-sdk/pull/7483
- [ ] https://github.com/paritytech/polkadot-sdk/pull/7357
- [ ] https://github.com/paritytech/polkadot-sdk/pull/7424
- [ ] https://github.com/paritytech/polkadot-staking-miner/pull/955

This branch can be periodically merged into
https://github.com/paritytech/polkadot-sdk/pull/7358 ->
https://github.com/paritytech/polkadot-sdk/pull/6996

## TODOs: 

- [x] rebase to master 
- Benchmarking for staking critical path
  - [x] snapshot
  - [x] election result
- Benchmarking for EPMB critical path
  - [x] snapshot
  - [x] verification
  - [x] submission
  - [x] unsigned submission
  - [ ] election results fetching
- [ ] Fix deletion weights. Either of
  - [ ] Garbage collector + lazy removal of all paged storage items
  - [ ] Confirm that deletion is small PoV footprint.
- [ ] Move election prediction to be push based. @tdimitrov 
- [ ] integrity checks for bounds 
- [ ] Properly benchmark this as a part of CI -- for now I will remove
them as they are too slow
- [x] add try-state to all pallets
- [x] Staking to allow genesis dev accounts to be created internally
- [x] Decouple miner config so @niklasad1 can work on the miner
72841b73
- [x] duplicate snapshot page reported by @niklasad1

 
- [ ] https://github.com/paritytech/polkadot-sdk/pull/6520 or equivalent
-- during snapshot, `VoterList` must be locked
- [ ] Move target snapshot to a separate block

---------

Co-authored-by: Gonçalo Pestana <g6pestana@gmail.com>
Co-authored-by: Ankan <10196091+Ank4n@users.noreply.github.com>
Co-authored-by: command-bot <>
Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>
Co-authored-by: Giuseppe Re <giuseppe.re@parity.io>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Changes:
- Expose a `force_set_head` function from the `MessageQueue` pallet via
a new trait: `ForceSetHead`. This can be used to force the MQ pallet to
process this queue next.
- The change only exposes an internal function through a trait, no audit
is required.

## Context

For the Asset Hub Migration (AHM) we need a mechanism to prioritize the
inbound upward messages and the inbound downward messages on the AH. To
achieve this, a minimal (and no breaking) change is done to the MQ
pallet in the form of adding the `force_set_head` function.

An example use of how to achieve prioritization is then demonstrated in
`integration_test.rs::AhmPrioritizer`. Normally, all queues are
scheduled round-robin like this:

`| Relay | Para(1) | Para(2) | ... | Relay | ... `

The prioritizer listens to changes to its queue and triggers if either:
- The queue processed in the last block (to keep the general round-robin
scheduling)
- The queue did not process since `n` blocks (to prevent starvation if
there are too many other queues)

In either situation, it schedules the queue for a streak of three
consecutive blocks, such that it would become:

`| Relay | Relay | Relay | Para(1) | Para(2) | ... | Relay | Relay |
Relay | ... `

It basically transforms the round-robin into an elongated round robin.
Although different strategies can be injected into the pallet at
runtime, this one seems to strike a good balance between general service
level and prioritization.

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: muharem <ismailov.m.h@gmail.com>

Closes #3270

---------

Co-authored-by: command-bot <>

Follow up from
https://github.com/paritytech/polkadot-sdk/pull/6362#issuecomment-2629744365

The goal of this PR is to have the scheduler pallet work on a parachain
which does not produce blocks on a regular schedule, thus can use the
relay chain as a block provider.

Because blocks are not produced regularly, we cannot make the assumption
that block number increases monotonically, and thus have new logic to
handle multiple spend periods passing between blocks.

Requirement: 

instead of using the hard coded system block number. We add an
associated type BlockNumberProvider

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Implementation of on-demand credits as described in
[RFC-1](https://github.com/polkadot-fellows/RFCs/blob/main/text/0001-agile-coretime.md#instantaneous-coretime)

---------

Co-authored-by: ordian <write@reusable.software>
Co-authored-by: Dónal Murray <donalm@seadanda.dev>

to zombienet-sdk 0.2.24 (also needed to update to this version for
slashing to work).

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Alexandru Vasile <60601340+lexnv@users.noreply.github.com>

# Description

Fixes #7039

The Preservation of transfer method of fungible and fungibles adapters
is changed from Preserve to Expendable. So the behavior of the
TransferAsset will be consistent with the WithdrawAsset function, as in
[fungible](https://github.com/paritytech/polkadot-sdk/blob/f3ab3854

/polkadot/xcm/xcm-builder/src/fungible_adapter.rs#L217)
and [fungibles](https://github.com/paritytech/polkadot-sdk/issues/url)
adapter.

This pull request includes changes to the `fungible_adapter.rs` and
`fungibles_adapter.rs` files in the `polkadot/xcm/xcm-builder`
directory. The main change involves modifying the transfer method to use
the `Expendable` strategy instead of the `Preserve` strategy.

Changes to transfer strategy:

*
[`polkadot/xcm/xcm-builder/src/fungible_adapter.rs`](diffhunk://#diff-6ebd77385441f2c8b023c480e818a01c4b43ae892c73ca30144cd64ee960bd66L67-R67):
Changed the transfer method to use `Expendable` instead of `Preserve`.
*
[`polkadot/xcm/xcm-builder/src/fungibles_adapter.rs`](diffhunk://#diff-82221429de4c4c88be3d2976ece6475ef4fa56a32abc70290911bd47191f8e17L61-R61):
Changed the transfer method to use `Expendable` instead of `Preserve`.

---------

Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: Adrian Catangiu <adrian@parity.io>

This PR introduces BlockNumberProvider config for the nomination pool
pallet.
closes part of https://github.com/paritytech/polkadot-sdk/issues/6297

approval-voting-parallel has been running on all network types except
polkadot since release `1.17.0`, so it has around 2 months of baking and
running without any reported issues, so let's enable it on polkadot as
well.

After running in polkadot for awhile the flag will be entirely removed.

---------

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

This PR introduces BlockNumberProvider config for the conviction voting
pallet.
closes part of https://github.com/paritytech/polkadot-sdk/issues/6297

---------

Co-authored-by: muharem <ismailov.m.h@gmail.com>
Co-authored-by: command-bot <>

There is a small issue on restart, where if finality is lagging across
session boundary and the validator restarts, then the validator won't be
able to contribute anymore with assginments/approvals and gossiping for
the blocks from the previous session, because after restart it builds
the Topology only for the new session, so without a topology it won't be
able to distribute assignments and approvals because everything in
`approval-distribution` is gated on having a topology for the block.

The fix is to also keep track of the last finalized block and its
session and if it is different from the list of encountered sessions,
build its topology and send it to the rest of subsystems.

---------

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>
Co-authored-by: ordian <write@reusable.software>

This PR introduces BlockNumberProvider config for pallet society.
closes part of https://github.com/paritytech/polkadot-sdk/issues/6297

- Closes https://github.com/paritytech/license-scanner/issues/44
- Silent because only comments are changed in the crates.

## What's inside

First, we change the file traversal mechanism from shell globbing to
walking through files which happens inside the `license-scanner` - so it
has knowledge about directory structure and can correlate files with
corresponding Cargo manifest.

Next, added `MIT-0` and `Unlicense` to the allowed list of licenses.
`Unlicense` appears only once across {Substrate,Cumulus,Polkadot} - in
`penpal-runtime`.

Finally, updated headers in files that do not match the corresponding
manifest license.

---------

Co-authored-by: cornholio <0@mcornholio.ru>

This PR introduces BlockNumberProvider config for the referenda pallet.
closes part of https://github.com/paritytech/polkadot-sdk/issues/6297

Polkadot address: 12GyGD3QhT4i2JJpNzvMf96sxxBLWymz4RdGCxRH5Rj5agKW

---------

Co-authored-by: muharem <ismailov.m.h@gmail.com>

This PR is centered around a main fix regarding the base deposit and a
bunch of drive by or related fixtures that make sense to resolve in one
go. It could be broken down more but I am constantly rebasing this PR
and would appreciate getting those fixes in as-one.

**This adds a multi block migration to Westend AssetHub that wipes the
pallet state clean. This is necessary because of the changes to the
`ContractInfo` storage item. It will not delete the child storage
though. This will leave a tiny bit of garbage behind but won't cause any
problems. They will just be orphaned.**

## Record the deposit for immutable data into the `storage_base_deposit`

The `storage_base_deposit` are all the deposit a contract has to pay for
existing. It included the deposit for its own metadata and a deposit
proportional (< 1.0x) to the size of its code. However, the immutable
code size was not recorded there. This would lead to the situation where
on terminate this portion wouldn't be refunded staying locked into the
contract. It would also make the calculation of the deposit changes on
`set_code_hash` more complicated when it updates the immutable data (to
be done in #6985). Reason is because it didn't know how much was payed
before since the storage prices could have changed in the mean time.

In order for this solution to work I needed to delay the deposit
calculation for a new contract for after the contract is done executing
is constructor as only then we know the immutable data size. Before, we
just charged this eagerly in `charge_instantiate` before we execute the
constructor. Now, we merely send the ED as free balance before the
constructor in order to create the account. After the constructor is
done we calculate the contract base deposit and charge it. This will
make `set_code_hash` much easier to implement.

As a side effect it is now legal to call `set_immutable_data` multiple
times per constructor (even though I see no reason to do so). It simply
overrides the immutable data with the new value. The deposit accounting
will be done after the constructor returns (as mentioned above) instead
of when setting the immutable data.

## Don't pre-charge for reading immutable data

I noticed that we were pre-charging weight for the max allowable
immutable data when reading those values and then refunding after read.
This is not necessary as we know its length without reading the storage
as we store it out of band in contract metadata. This makes reading it
free. Less pre-charging less problems.

## Remove delegate locking

Fixes #7092

This is also in the spirit of making #6985 easier to implement. The
locking complicates `set_code_hash` as we might need to block settings
the code hash when locks exist. Check #7092 for further rationale.

## Enforce "no terminate in constructor" eagerly

We used to enforce this rule after the contract execution returned. Now
we error out early in the host call. This makes it easier to be sure to
argue that a contract info still exists (wasn't terminated) when a
constructor successfully returns. All around this his just much simpler
than dealing this check.

## Moved refcount functions to `CodeInfo`

They never really made sense to exist on `Stack`. But now with the
locking gone this makes even less sense. The refcount is stored inside
`CodeInfo` to lets just move them there.

## Set `CodeHashLockupDepositPercent` for test runtime

The test runtime was setting `CodeHashLockupDepositPercent` to zero.
This was trivializing many code paths and excluded them from testing. I
set it to `30%` which is our default value and fixed up all the tests
that broke. This should give us confidence that the lockup doeposit
collections properly works.

## Reworked the `MockExecutable` to have both a `deploy` and a `call`
entry point

This type used for testing could only have either entry points but not
both. In order to fix the `immutable_data_set_overrides` I needed to a
new function `add_both` to `MockExecutable` that allows to have both
entry points. Make sure to make use of it in the future :)

---------

Co-authored-by: command-bot <>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: PG Herveou <pgherveou@gmail.com>
Co-authored-by: Bastian Köcher <git@kchr.de>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Part of https://github.com/paritytech/polkadot-sdk/issues/5079.

Removes all usage of the static async backing params, replacing them
with dynamically computed equivalent values (based on the claim queue
and scheduling lookahead).

Adds a new runtime API for querying the scheduling lookahead value. If
not present, falls back to 3 (the default value that is backwards
compatible with values we have on production networks for
allowed_ancestry_len)

Also resolves most of
https://github.com/paritytech/polkadot-sdk/issues/4447, removing code
that handles async backing not yet being enabled.
While doing this, I removed the support for collation protocol version 1
on collators, as it only worked for leaves not supporting async backing
(which are none).
I also unhooked the legacy v1 statement-distribution (for the same
reason as above). That subsystem is basically dead code now, so I had to
remove some of its tests as they would no longer pass (since the
subsystem no longer sends messages to the legacy variant). I did not
remove the entire legacy subsystem yet, as that would pollute this PR
too much. We can remove the entire v1 and v2 validation protocols in a
follow up PR.

In another PR: remove test files with names `prospective_parachains`
(it'd pollute this PR if we do now)

TODO:
- [x] add deprecation warnings
- [x] prdoc

---------

Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

This PR backports regular version bumps and prdoc reorganization from
stable release branch back to master

This should fix the error log related to PoV pre-dispatch weight being
lower than post-dispatch for `ParasInherent`:
```
ERROR tokio-runtime-worker runtime::frame-support: Post dispatch weight is greater than pre dispatch weight. Pre dispatch weight may underestimating the actual weight. Greater post dispatch weight components are ignored.
                                        Pre dispatch weight: Weight { ref_time: 47793353978, proof_size: 1019 },
                                        Post dispatch weight: Weight { ref_time: 5030321719, proof_size: 135395 }
```

---------

Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>

malus-collator: implement malicious collator submitting same collation to all backing groups (#6924)

## Issues
- [[#5049] Elastic scaling: zombienet
tests](https://github.com/paritytech/polkadot-sdk/issues/5049)
- [[#4526] Add zombienet tests for malicious
collators](https://github.com/paritytech/polkadot-sdk/issues/4526)

## Description
Modified the undying collator to include a malus mode, in which it
submits the same collation to all assigned backing groups.

## TODO
* [X] Implement malicious collator that submits the same collation to
all backing groups;
* [X] Avoid the core index check in the collation generation subsystem:
https://github.com/paritytech/polkadot-sdk/blob/master/polkadot/node/collation-generation/src/lib.rs#L552-L553;
* [X] Resolve the mismatch between the descriptor and the commitments
core index: https://github.com/paritytech/polkadot-sdk/pull/7104
* [X] Implement `duplicate_collations` test with zombienet-sdk;
* [X] Add PRdoc.

# Description

Close #7122.

This PR replaces the unmaintained `derivative` dependency with
`derive-where`.

## Integration

This PR doesn't change the public interfaces.

## Review Notes

The `derivative` crate, previously used to derive basic traits for
structs with generics or enums, is no longer actively maintained. It has
been replaced with the `derive-where` crate, which offers a more
straightforward syntax while providing the same features as
`derivative`.

---------

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

Closes #216.

This PR allows pallets to define a `view_functions` impl like so:

```rust
#[pallet::view_functions]
impl<T: Config> Pallet<T>
where
	T::AccountId: From<SomeType1> + SomeAssociation1,
{
	/// Query value no args.
	pub fn get_value() -> Option<u32> {
		SomeValue::<T>::get()
	}

	/// Query value with args.
	pub fn get_value_with_arg(key: u32) -> Option<u32> {
		SomeMap::<T>::get(key)
	}
}
```
### `QueryId`

Each view function is uniquely identified by a `QueryId`, which for this
implementation is generated by:

```twox_128(pallet_name) ++ twox_128("fn_name(fnarg_types) -> return_ty")```

The prefix `twox_128(pallet_name)` is the same as the storage prefix for pallets and take into account multiple instances of the same pallet.

The suffix is generated from the fn type signature so is guaranteed to be unique for that pallet impl. For one of the view fns in the example above it would be `twox_128("get_value_with_arg(u32) -> Option<u32>")`. It is a known limitation that only the type names themselves are taken into account: in the case of type aliases the signature may have the same underlying types but a different id; for generics the concrete types may be different but the signatures will remain the same.

The existing Runtime `Call` dispatchables are addressed by their concatenated indices `pallet_index ++ call_index`, and the dispatching is handled by the SCALE decoding of the `RuntimeCallEnum::PalletVariant(PalletCallEnum::dispatchable_variant(payload))`. For `view_functions` the runtime/pallet generated enum structure is replaced by implementing the `DispatchQuery` trait on the outer (runtime) scope, dispatching to a pallet based on the id prefix, and the inner (pallet) scope dispatching to the specific function based on the id suffix.

Future implementations could also modify/extend this scheme and routing to pallet agnostic queries.

### Executing externally

These view functions can be executed externally via the system runtime api:

```rust
pub trait ViewFunctionsApi<QueryId, Query, QueryResult, Error> where
	QueryId: codec::Codec,
	Query: codec::Codec,
	QueryResult: codec::Codec,
	Error: codec::Codec,
{
	/// Execute a view function query.
fn execute_query(query_id: QueryId, query: Query) -> Result<QueryResult,
Error>;
}
```
### `XCQ`
Currently there is work going on by @xlc to implement [`XCQ`](https://github.com/open-web3-stack/XCQ/) which may eventually supersede this work.

It may be that we still need the fixed function local query dispatching in addition to XCQ, in the same way that we have chain specific runtime dispatchables and XCM.

I have kept this in mind and the high level query API is agnostic to the underlying query dispatch and execution. I am just providing the implementation for the `view_function` definition.

### Metadata
Currently I am utilizing the `custom` section of the frame metadata, to avoid modifying the official metadata format until this is standardized.

### vs `runtime_api`
There are similarities with `runtime_apis`, some differences being:
- queries can be defined directly on pallets, so no need for boilerplate declarations and implementations
- no versioning, the `QueryId` will change if the signature changes. 
- possibility for queries to be executed from smart contracts (see below)

### Calling from contracts
Future work would be to add `weight` annotations to the view function queries, and a host function to `pallet_contracts` to allow executing these queries from contracts.

### TODO

- [x] Consistent naming (view functions pallet impl, queries, high level api?)
- [ ] End to end tests via `runtime_api`
- [ ] UI tests
- [x] Mertadata tests
- [ ] Docs

---------

Co-authored-by: kianenigma <kian@parity.io>
Co-authored-by: James Wilson <james@jsdw.me>
Co-authored-by: Giuseppe Re <giuseppe.re@parity.io>
Co-authored-by: Guillaume Thiolliere <guillaume.thiolliere@parity.io>

On top of https://github.com/paritytech/polkadot-sdk/pull/6757

Fixes https://github.com/paritytech/polkadot-sdk/issues/6858 by bumping
the `PARENT_SEARCH_DEPTH` constant to a larger value (30) and adds a
zombienet-sdk test that exercises the 12-core scenario.

This is a node-side limit that restricts the number of allowed pending
availability candidates when choosing the parent parablock during
authoring.
This limit is rather redundant, as the parachain runtime already
restricts the unincluded segment length to the configured value in the
[FixedVelocityConsensusHook](https://github.com/paritytech/polkadot-sdk/blob/88d900af

/cumulus/pallets/aura-ext/src/consensus_hook.rs#L35)
(which ideally should be equal to this `PARENT_SEARCH_DEPTH`).

For 12 cores, a value of 24 should be enough, but I bumped it to 30 to
have some extra buffer.

There are two other potential ways of fixing this:
- remove this constant altogether, as the parachain runtime already
makes those guarantees. Chose not to do this, as it can't hurt to have
an extra safeguard
- set this value to be equal to the uninlcuded segment size. This value
however is not exposed to the node-side and would require a new runtime
API, which seems overkill for a redundant check.

---------

Co-authored-by: Javier Viola <javier@parity.io>

Resolves (partially):
https://github.com/paritytech/polkadot-sdk/issues/7148 (see _Problem 1 -
`ShouldExecute` tuple implementation and `Deny` filter tuple_)

This PR changes the behavior of `DenyThenTry` from the pattern
`DenyIfAllMatch` to `DenyIfAnyMatch` for the tuple.

I would expect the latter is the right behavior so make the fix in
place, but we can also add a dedicated Impl with the legacy one
untouched.

## TODO
- [x] add unit-test for `DenyReserveTransferToRelayChain`
- [x] add test and investigate/check `DenyThenTry` as discussed
[here](https://github.com/paritytech/polkadot-sdk/pull/6838#discussion_r1914553990)
and update documentation if needed

---------

Co-authored-by: Branislav Kontur <bkontur@gmail.com>
Co-authored-by: Francisco Aguirre <franciscoaguirreperez@gmail.com>
Co-authored-by: command-bot <>
Co-authored-by: Clara van Staden <claravanstaden64@gmail.com>
Co-authored-by: Adrian Catangiu <adrian@parity.io>

#Description
Migrated polkadot-runtime-parachains slots benchmarking to the new
benchmarking syntax v2.
This is part of #6202

---------

Co-authored-by: Giuseppe Re <giuseppe.re@parity.io>
Co-authored-by: seemantaggarwal <32275622+seemantaggarwal@users.noreply.github.com>
Co-authored-by: Bastian Köcher <git@kchr.de>

Part of: https://github.com/paritytech/polkadot-sdk/issues/6906

Closes #6196 
Closes #7204

Example of PR: https://github.com/paritytech/polkadot-sdk/pull/6816

Every sunday 01:00 AM it's going to start to benchmark (with /cmd bench)
all runtimes and all pallets
Then diff total will be pushed to a branch and PR open,. I assume
review-bot is going assign required reviewers per changed files

I afraid each weeks will be too much to review & merge, but we can
adjust later

Bonus: fix for pallet_multisig lib and
substrate/.maintain/frame-weight-template.hbs , which didn't let to
compile new weights

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: command-bot <>
Co-authored-by: cmd[bot] <41898282+github-actions[bot]@users.noreply.github.com>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Currently the `para_backing_state` API is used only by the prospective
parachains subsystems and returns 2 things: the constraints for
parachain blocks and the candidates pending availability.

This PR deprecates `para_backing_state` and introduces a new
`backing_constraints` API that can be used together with
`candidates_pending_availability` to get the same information provided
by `para_backing_state`.

TODO:
- [x] PRDoc

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Signed-off-by: Andrei Sandu <andrei-mihail@parity.io>
Co-authored-by: command-bot <>

This is the right value after
https://github.com/paritytech/polkadot-sdk/pull/4880, which corresponds
to an allowedAncestryLen of 2 (which is the default)

WIll fix https://github.com/paritytech/polkadot-sdk/issues/7105

This PR contains small fixes identified during work on the larger PR:
https://github.com/paritytech/polkadot-sdk/issues/6906.

---------

Co-authored-by: command-bot <>