[wip] Replace era-specific PParams serializers with instances defined in EraPParams

[teodanciu]

Description

These are changes to be merged in my other branch, refactor-pparams.

The reason for this structure with two PRs is as follows:

1. refactor-pparams brand and PR just adds functions equivalent to the CBOR, JSON and Plutus (de)serializers, and also adds tests to check the equivalence, but doesn't actually replace the instances. So that both versions (the current (de)serializers) and the new versions exists at the same time and their equivalence is checked by CI by running these tests I added

2. we want the final changes to replace the instances with the functions I added in refactor-pparams, and this is what this PR does: defining generic instances in EraPParams and using them in the instances of each era. Also removing the temporary tests.

Checklist

• Commits in meaningful sequence and with useful messages.
• Tests added or updated when needed.
• CHANGELOG.md files updated for packages with externally visible changes.
  NOTE: New section is never added with the code changes. (See RELEASING.md).
• Versions updated in .cabal and CHANGELOG.md files when necessary, according to the
  versioning process.
• Version bounds in .cabal files updated when necessary.
  NOTE: If bounds change in a cabal file, that package itself must have a version increase. (See RELEASING.md).
• Code formatted (use scripts/fourmolize.sh).
• Cabal files formatted (use scripts/cabal-format.sh).
• CDDL files are up to date (use scripts/gen-cddl.sh)
• hie.yaml updated (use scripts/gen-hie.sh).
• Self-reviewed the diff.

[teodanciu]

Superseded by #5027