DRep expiry update after a contiguous set of epochs with no proposals to vote on

[aniketd]

Description

Closes #3723

1. Add vsNumDormantEpochs field to VState.
   1. This field counts the number of contiguous epochs in which the number of active governance proposals that can be voted on remained zero. It will be incremented in every EPOCH if the number of active governance actions that can be voted on continues to remain zero. It will be reset when a new governance proposal is submitted successfully
2. Prevent DRep expiry when no proposals to vote on.
   1. In EPOCH, we make sure to update the dormant-epochs counter every time we see that the previous epoch didn't have any governance proposals to vote on.
   2. When there is a new governance proposal in a transaction AND the dormant-epochs counter is greater than zero, we
      1. Update the expiry for all DReps by adding the counter
      2. Reset the dormant-epochs counter
   3. We update Api.State.Query.queryDRepState to report the effective DRep expiry information.
   4. Add snapshotsGovStateL to ConwayEraGov
   5. Move asks out of loop in GO
3. Add ConwayFeatures test for preventing DRep expiry

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated
• When applicable, versions are updated in .cabal and CHANGELOG.md files according to the
  versioning process.
• The version bounds in .cabal files for all affected packages are updated. If you change the bounds in a cabal file, that package itself must have a version increase. (See RELEASING.md)
• All visible changes are prepended to the latest section of a CHANGELOG.md for the affected packages. New section is never added with the code changes. (See RELEASING.md)
• Code is formatted with fourmolu (use scripts/fourmolize.sh)
• Cabal files are formatted (use scripts/cabal-format.sh)
• hie.yaml has been updated (use scripts/gen-hie.sh)
• Self-reviewed the diff

[Soupstraw]

Good job!

[lehins]

Very nice!!! 👍

[lehins]

@aniketd Needs golden test adjustment, since we added a new field and some other test failures. Not sure what they are about

[lehins]

Beautiful! 🙂