Preparation for https://github.com/paritytech/polkadot-sdk/pull/3935

Changes:
- Add some `default-features = false` for the case that a crate and that
dependency both support nostd builds.
- Shuffle files around of some benchmarking-only crates. These
conditionally disabled the `cfg_attr` for nostd and pulled in libstd.
Example [here](https://github.com/ggwpez/zepter/pull/95). The actual
logic is moved into a `inner.rs` to preserve nostd capability of the
crate in case the benchmarking feature is disabled.
- Add some `use sp_std::vec` where needed.
- Remove some `optional = true` in cases where it was not optional.
- Removed one superfluous `cfg_attr(not(feature = "std"), no_std..`.

All in all this should be logical no-op.

---------

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

helps https://github.com/paritytech/polkadot-sdk/issues/439.
closes https://github.com/paritytech/polkadot-sdk/issues/473.

PR link in the older substrate repository:
https://github.com/paritytech/substrate/pull/13498.

# Context
Rewards payout is processed today in a single block and limited to
`MaxNominatorRewardedPerValidator`. This number is currently 512 on both
Kusama and Polkadot.

This PR tries to scale the nominators payout to an unlimited count in a
multi-block fashion. Exposures are stored in pages, with each page
capped to a certain number (`MaxExposurePageSize`). Starting out, this
number would be the same as `MaxNominatorRewardedPerValidator`, but
eventually, this number can be lowered through new runtime upgrades to
limit the rewardeable nominators per dispatched call instruction.

The changes in the PR are backward compatible.

## How payouts would work like after this change
Staking exposes two calls, 1) the existing `payout_stakers` and 2)
`payout_stakers_by_page`.

### payout_stakers
This remains backward compatible with no signature change. If for a
given era a validator has multiple pages, they can call `payout_stakers`
multiple times. The pages are executed in an ascending sequence and the
runtime takes care of preventing double claims.

### payout_stakers_by_page
Very similar to `payout_stakers` but also accepts an extra param
`page_index`. An account can choose to payout rewards only for an
explicitly passed `page_index`.

**Lets look at an example scenario**
Given an active validator on Kusama had 1100 nominators,
`MaxExposurePageSize` set to 512 for Era e. In order to pay out rewards
to all nominators, the caller would need to call `payout_stakers` 3
times.

- `payout_stakers(origin, stash, e)` => will pay the first 512
nominators.
- `payout_stakers(origin, stash, e)` => will pay the second set of 512
nominators.
- `payout_stakers(origin, stash, e)` => will pay the last set of 76
nominators.
...
- `payout_stakers(origin, stash, e)` => calling it the 4th time would
return an error `InvalidPage`.

The above calls can also be replaced by `payout_stakers_by_page` and
passing a `page_index` explicitly.

## Commission note
Validator commission is paid out in chunks across all the pages where
each commission chunk is proportional to the total stake of the current
page. This implies higher the total stake of a page, higher will be the
commission. If all the pages of a validator's single era are paid out,
the sum of commission paid to the validator across all pages should be
equal to what the commission would have been if we had a non-paged
exposure.

### Migration Note
Strictly speaking, we did not need to bump our storage version since
there is no migration of storage in this PR. But it is still useful to
mark a storage upgrade for the following reasons:

- New storage items are introduced in this PR while some older storage
items are deprecated.
- For the next `HistoryDepth` eras, the exposure would be incrementally
migrated to its corresponding paged storage item.
- Runtimes using staking pallet would strictly need to wait at least
`HistoryDepth` eras with current upgraded version (14) for the migration
to complete. At some era `E` such that `E >
era_at_which_V14_gets_into_effect + HistoryDepth`, we will upgrade to
version X which will remove the deprecated storage items.
In other words, it is a strict requirement that E<sub>x</sub> -
E<sub>14</sub> > `HistoryDepth`, where
E<sub>x</sub> = Era at which deprecated storages are removed from
runtime,
E<sub>14</sub> = Era at which runtime is upgraded to version 14.
- For Polkadot and Kusama, there is a [tracker
ticket](https://github.com/paritytech/polkadot-sdk/issues/433) to clean
up the deprecated storage items.

### Storage Changes

#### Added
- ErasStakersOverview
- ClaimedRewards
- ErasStakersPaged

#### Deprecated
The following can be cleaned up after 84 eras which is tracked
[here](https://github.com/paritytech/polkadot-sdk/issues/433).

- ErasStakers.
- ErasStakersClipped.
- StakingLedger.claimed_rewards, renamed to
StakingLedger.legacy_claimed_rewards.

### Config Changes
- Renamed MaxNominatorRewardedPerValidator to MaxExposurePageSize.

### TODO
- [x] Tracker ticket for cleaning up the old code after 84 eras.
- [x] Add companion.
- [x] Redo benchmarks before merge.
- [x] Add Changelog for pallet_staking.
- [x] Pallet should be configurable to enable/disable paged rewards.
- [x] Commission payouts are distributed across pages.
- [x] Review documentation thoroughly.
- [x] Rename `MaxNominatorRewardedPerValidator` ->
`MaxExposurePageSize`.
- [x] NMap for `ErasStakersPaged`.
- [x] Deprecate ErasStakers.
- [x] Integrity tests.

### Followup issues
[Runtime api for deprecated ErasStakers storage
item](https://github.com/paritytech/polkadot-sdk/issues/426)

---------

Co-authored-by: Javier Viola <[email protected]>
Co-authored-by: Ross Bulat <[email protected]>
Co-authored-by: command-bot <>

* Remove use of trait Store from staking pallet

* Remove use of trait Store from bounties pallet

* Remove use of trait Store from collective pallet

* Remove use of trait Store from babe pallet

* Remove use of trait Store from assets pallet

* Remove use of trait Store from grandpa pallet

* Remove use of trait Store from balances pallet

* Remove use of trait Store from authorship pallet

* Remove use of trait Store from authority-discovery pallet

* Remove use of trait Store from atomic-swap pallet

* Remove use of trait Store from sudo pallet

* Remove use of trait Store from scheduler pallet

* Remove use of trait Store from scored-pool pallet

* Remove use of trait Store from society pallet

* Remove use of trait Store from lottery pallet

* Remove use of trait Store from executive pallet

* Remove use of trait Store from democracy pallet

* Remove use of trait Store from elections-phragmen pallet

* Remove use of trait Store from indices pallet

* Remove use of trait Store from identity pallet

* Remove use of trait Store from multisig pallet

* Remove use of trait Store from merkle-mountain-range pallet

* Remove use of trait Store from im-online pallet

* Remove use of trait Store from membership pallet

* Remove use of trait Store from nicks pallet

* Remove use of trait Store from session pallet

* Remove use of trait Store from transaction-payment pallet

* Remove use of trait Store from utility pallet

* Remove use of trait Store from child-bounties pallet

* Remove use of trait Store from nis pallet

* Remove use of trait Store from nfts pallet

* Remove use of trait Store from conviction-voting pallet

* Remove use of trait Store from treasury pallet

* Remove use of trait Store from vesting pallet

* Remove use of trait Store from preimage pallet

* Remove use of trait Store from uniques pallet

* Remove use of trait Store from ranked-collective pallet

* Remove use of trait Store from beefy-mmr pallet

* Remove use of trait Store from referenda pallet

* Remove use of trait Store from whitelist pallet

* Remove use of trait Store from alliance pallet

* Remove use of trait Store from nomination-pools pallet

* Remove use of trait Store from state-trie-migration pallet

* Remove use of trait Store from message-queue pallet

* Remove use of trait Store from root-offences pallet

* Remove use of trait Store from root-testing pallet

* Remove use of trait Store from timestamps pallet

* Remove use of trait Store from system pallet

* Remove use of trait Store from offences pallet

* Remove use of trait Store from recovery pallet

* Remove use of trait Store from node-authorization pallet

* Remove use of trait Store from proxy pallet

* Remove use of trait Store from benchmarking pallet

* Remove use of trait Store from bags-list pallet

* Add deprecated warning in store_trait

* Change warning message

* Run cargo fmt

* Fix warning and update tests

* Remove unnecessary allow deprecated

* Remove use of trait Store

* Fix mismatch in expected output

* Minor update to warning message for deprecation of generate_store with Store trait attribute

* Fixes as per review comments

* Fixes as per review suggestions

* Remove use of Store trait from core-fellowship pallet

* Fix type in store_trait.rs

* Fixes as pre review comment

* Change copyright year to 2023 from 2022

* Fix incorrect update of copyright year

* Remove years from copy right header

* Fix remaining files

* Fix typo in a header and remove update-copyright.sh

* frame-system: explicit call index

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

* Use explicit call indices

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

* pallet-template: explicit call index

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

* DNM: Temporarily require call_index

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

* Revert "DNM: Temporarily require call_index"

This reverts commit c4934e312e12af72ca05a8029d7da753a9c99346.

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

* Move fill_block to RootOffences

* docs

* new pallet

* new line

* fix

* Update frame/root-testing/src/lib.rs

Co-authored-by: Bastian Köcher <[email protected]>

* Update frame/root-testing/src/lib.rs

Co-authored-by: Bastian Köcher <[email protected]>

* Update bin/node/runtime/src/lib.rs

Co-authored-by: Bastian Köcher <[email protected]>

* Update frame/root-testing/src/lib.rs

Co-authored-by: Bastian Köcher <[email protected]>

* Update frame/root-testing/src/lib.rs

Co-authored-by: Bastian Köcher <[email protected]>

* Update frame/root-testing/src/lib.rs

Co-authored-by: Bastian Köcher <[email protected]>

* fixes

* problem solved

* revert

* fix dependency

* hopefully making the CI happy

* ...

* dummy call

* remove dummy

* fix warning

Co-authored-by: Bastian Köcher <[email protected]>

* root-offences pallet

* fix errors

* cleaned up a bit

* remove unwrap()

* new pallet is getting compiled

* remove unnecessary type annotations

* remove more unnecessary type annotations

* addidtional cleaning

* commit

* cleaned up

* fix in logic

* add event

* removed Clone trait from AccountId

* test module

* remove unused imports

* fmt

* fix

* separate into functions, still messy

* test

* first test

* fmt

* cleaned up a bit

* separate into mock.rs and tests.rs

* basic docs for now

* pallet_staking GenesisiConfig

* fix

* added start_session

* passing tests

* impl GenesisConfig for pallet_session

* updated event

* Update frame/root-offences/src/lib.rs

Co-authored-by: Kian Paimani <[email protected]>

* Update frame/root-offences/src/lib.rs

Co-authored-by: Kian Paimani <[email protected]>

* remove <T: Config

* specifying trait bounds inside Config

* commit

* active era increases correctly :)

* ExtBuilder

* slashing works

* new test

* additional test

* commit

* order

* fix?

* fix in logic

* remove unnecessary

* wrap comment at 100

* fmt

* merge fixes

* Update frame/root-offences/src/lib.rs

Co-authored-by: Kian Paimani <[email protected]>

* Update frame/root-offences/src/lib.rs

Co-authored-by: Kian Paimani <[email protected]>

* docs

* Update frame/root-offences/README.md

Co-authored-by: Andronik <[email protected]>

* Update frame/root-offences/Cargo.toml

Co-authored-by: Andronik <[email protected]>

* license header

Co-authored-by: Kian Paimani <[email protected]>
Co-authored-by: Andronik <[email protected]>