Validate previously enacted govAction

[teodanciu]

Description

Closes #3656

• EnactState: store the last enacted GovId for each of the 4 types of actions for which it is relevant (corresponding to GovActionPurpose)
• Ratify: check that the previous govId that we have from the proposal matches the one that we store in the enact state.
  If it doesn't match, we "drop" the signal (we don't enact it and it will eventually expire)
• Enact: when enacting, update the stored value for last govId

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]

Perfect with the respect to logic. Let's converge on the naming and this will be good to be merged

[lehins]

Perfect! Thank you!