Remove EnactState from ConwayGovState

[Soupstraw]

Description

This PR removes the EnactState field from ConwayGovState. The fields that have to be stored in the state are copied over to the ConwayGovState.

Since we're not storing the whole enact state in the ledger state any more, we don't have to check the invariants in the EPOCH rule.

resolves #3998

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

[lehins]

This is great. Exactly what we needed

Thank you.

[aniketd]

Grand! 🙌