closes https://github.com/paritytech/polkadot-sdk/issues/1882



## Breaking Changes

This PR introduces a new item to `pallet_balances::Config`:

```diff
trait Config {
++    type RuntimeFreezeReasons;
}
```

This value is only used to check it against `type MaxFreeze`. A similar
check has been added for `MaxHolds` against `RuntimeHoldReasons`, which
is already given to `pallet_balances`.

In all contexts, you should pass the real `RuntimeFreezeReasons`
generated by `construct_runtime` to `type RuntimeFreezeReasons`. Passing
`()` would also work, but it would imply that the runtime uses no
freezes at all.

---------

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

The runtime code of a parachain can be replaced on the relay-chain via:

[cumulus]:
[enact_authorized_upgrade](https://github.com/paritytech/polkadot-sdk/blob/1a38d6d6be42b30e8be3ffccec75a4ec995fef9d/cumulus/pallets/parachain-system/src/lib.rs#L661);
this is used for a runtime upgrade when a parachain is not bricked.

[polkadot] (these are used when a parachain is bricked):
-
[force_set_current_code](https://github.com/paritytech/polkadot-sdk/blob/1a38d6d6be42b30e8be3ffccec75a4ec995fef9d/polkadot/runtime/parachains/src/paras/mod.rs#L823):
immediately changes the runtime code of a given para without a pvf check
(root).
-
[force_schedule_code_upgrade](https://github.com/paritytech/polkadot-sdk/blob/1a38d6d6be42b30e8be3ffccec75a4ec995fef9d/polkadot/runtime/parachains/src/paras/mod.rs#L864):
schedules a change to the runtime code of a given para including a pvf
check of the new code (root).
-
[schedule_code_upgrade](https://github.com/paritytech/polkadot-sdk/blob/1a38d6d6be42b30e8be3ffccec75a4ec995fef9d/polkadot/runtime/common/src/paras_registrar.rs#L395):
schedules a change to the runtime code of a given para including a pvf
check of the new code. Besides root, the parachain or parachain manager
can call this extrinsic given that the parachain is unlocked.

Polkadot signals a parachain to be ready for a runtime upgrade through
the
[GoAhead](https://github.com/paritytech/polkadot-sdk/blob/e49493442a9377be9344c06a4990e17423783d41/polkadot/primitives/src/v5/mod.rs#L1229)
signal.

When in cumulus `enact_authorized_upgrade` is executed, the same
underlying helper function of `force_schedule_code_upgrade` &
`schedule_code_upgrade`:
[schedule_code_upgrade](https://github.com/paritytech/polkadot/blob/09b61286da11921a3dda0a8e4015ceb9ef9cffca/runtime/parachains/src/paras/mod.rs#L1778),
is called on the relay-chain, which sets the `GoAhead` signal (if the
pvf is accepted).

If Cumulus receives the `GoAhead` signal from polkadot without having
the `PendingValidationCode` ready, it will panic
([ref](https://github.com/paritytech/polkadot/pull/7412)). For
`enact_authorized_upgrade` we know for sure the `PendingValidationCode`
is set. On the contrary, for `force_schedule_code_upgrade` &
`schedule_code_upgrade` this is not the case.

This PR includes a flag such that the `GoAhead` signal will only be set
when a runtime upgrade is enacted by the parachain
(`enact_authorized_upgrade`).

additional info: https://github.com/paritytech/polkadot/pull/7412



Closes #641

---------

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

`VersionedMigration` has become somewhat widely used for handling
version bumps in migrations the last few months.

It is currently behind the `experimental` feature flag, requiring every
pallet that writes a new migration with version bumps to set up the
`experimental` flag in their own Cargo.tomls, and also for every runtime
using these pallets to explicitly enable the `experimental` flag for
each pallet.

This is becoming quite verbose, and I can only see the number of pallets
requiring the experimental flag increasing for no other reason than
using what has become a commonly used feature.

Additionally, I'm writing migration docs and would like to avoid
stepping through how to use the `experimental` feature to get
`VersionedMigration` working.

Since the feature has been used in production for some time now without
any reported issues, is becoming commonly used and ready to advertise in
docs, I feel this is a good time to make it non-experimental.

* rfc14

* Update polkadot/runtime/common/src/paras_registrar/mod.rs

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

* Update polkadot/runtime/common/src/paras_registrar/mod.rs

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

* Update polkadot/runtime/common/src/paras_registrar/mod.rs

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

* fmt

* fix

* Update polkadot/runtime/common/src/paras_registrar/migration.rs

Co-authored-by: Oliver Tale-Yazdi <[email protected]>

* fmt

* 2224 is unlocked

* update migration list

* update comment

* use VersionedMigration

---------

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