Make IsXXXBasedEra a class hierarchy

[Swordlash]

Changelog

- description: |
   Make `IsXXXBasedEra` a class hierarchy
  type:
  - compatible

Context

The PR makes IsXXXBasedEra a class hierarchy of one era being based of the next. I was surprised it's not the case in the code; I need to create a lot of dummy proofs like

maryFromAlonzo :: IsAlonzoBasedEra era => (IsMaryBasedEra era => a) -> a

in my projects.

How to trust this PR

It's a QOL improvement, just explicitly states a true fact of eras forming a chain.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• New tests are added if needed and existing tests are updated. See Running tests for more details
• Self-reviewed the diff

[carbolymer]

Thanks!

[Swordlash]

@carbolymer can you reapprove? I had an unverified commit, should be good now.