fix: runtime upgrade utils and migrations

[kylezs]

Closes: PRO-976

Pull Request

Checklist

Please conduct a thorough self-review before opening the PR.

• I am confident that the code works. - I wrote a dummy migration with passing and failing hooks and this works as expected.
• I have updated documentation where appropriate.

Summary

Somewhere at some point parity changed the way migrations run and ought to be run, and this changes it to run as parity runs them now.

The VersionedMigration struct that we have will eventually be replaced by the version included in polkadot-sdk here: paritytech/polkadot-sdk@4137aa6 once we upgrade to a version that includes it.

[codecov]

Codecov Report

Attention: 14 lines in your changes are missing coverage. Please review.

Comparison is base (9e20bc3) 72% compared to head (2bfb570) 72%.
Report is 3 commits behind head on main.

Files	Patch %	Lines
state-chain/runtime-upgrade-utilities/src/lib.rs	0%	14 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #4258   +/-   ##
=====================================
- Coverage     72%     72%   -0%     
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  Files        384     385    +1     
  Lines      63571   63487   -84     
  Branches   63571   63487   -84     
=====================================
- Hits       45482   45404   -78     
+ Misses     15749   15740    -9     
- Partials    2340    2343    +3     

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[linear]

PRO-976 Pre/Post runtime upgrade checks are not applied

Parity changed how the runtime upgrade checks are called, and as a consequence, the pre/post upgrade checks of tuples of runtime upgrades are no-ops(!). The solution that in the pallets, instead of overriding pre/post upgrade checks in the hooks, we should override the try_on_runtime_upgrade method. Basically:

fn try_on_rutime_upgrade(..) {
  VersionMigration::<T>::try_on_runtime_updrade(..)
}

As part of this, the README.md in the runtime upgrade utilities should also be updated.

Any old migrations can be deleted.

IMO we might as well keep the boilerplate and use type VersionedMigration = (); or similar if none are currently defined.