Add GovInfoEvent and add event testing capabilities to ImpTest

[Soupstraw]

Description

This PR adds an event to EPOCH which contains sets with expired and enacted governance actions and a set with all the governance action IDs that are unclaimed.

I also added a way to write tests about events and cleaned up Conway events. The ConwayUtxosEventis necessary because we have to get rid of PPUP events in Conway as we no longer have a PPUP rule.

resolves #4165

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

[teodanciu]

Will finish reviewing tomorrow, there's a lot here! (some of it above my head)

[teodanciu]

I still don't understand what we wouldn't be able to do without the new EraRuleEvent ( I don't even see any type annotations being removed, if anything, we seem to have added more , like going from:
mapM_ (tellEvent . SuccessfulPlutusScriptsEvent) (nonEmpty ps) to mapM_ (tellEvent . injectEvent @"UTXOS" . SuccessfulPlutusScriptsEvent @era) (nonEmpty ps), for example ),
but I can tell it's the technique used for EraRuleFailure, so I'll approve and hope to understand better one day.

[Soupstraw]

I still don't understand what we wouldn't be able to do without the new EraRuleEvent ( I don't even see any type annotations being removed, if anything, we seem to have added more , like going from: mapM_ (tellEvent . SuccessfulPlutusScriptsEvent) (nonEmpty ps) to mapM_ (tellEvent . injectEvent @"UTXOS" . SuccessfulPlutusScriptsEvent @era) (nonEmpty ps), for example ), but I can tell it's the technique used for EraRuleFailure, so I'll approve and hope to understand better one day.

The main point for adding EraRuleEvent is to enable using injectEvent. Without it we'd run into the same issue that #4071 was solving, but with events. This injectEvent will be useful for writing tests and also makes it easier to reuse existing rules in future eras. It's a bit of an ugly solution, but we should be able to make it better when we refactor after Conway.