Fix EraCast Certificate

[newhoggy]

Changelog

- description: |
    Fix `EraCast Certificate`
  compatibility: no-api-changes
  type: bugfix

Context

EraCast Certificate needs to be able to cast certificates between eras.

In future, the ledger will support this, however it is not available at the moment.

This PR implements the logic in cardano-api.

Checklist

• Commit sequence broadly makes sense and commits have useful messages
• The change log section in the PR description has been filled in
• New tests are added if needed and existing tests are updated. These may include:
  • golden tests
  • property tests
  • roundtrip tests
• The version bounds in .cabal files are updated
• CI passes. See note on CI. The following CI checks are required:
  • Code is linted with hlint. See .github/workflows/check-hlint.yml to get the hlint version
  • Code is formatted with stylish-haskell. See .github/workflows/stylish-haskell.yml to get the stylish-haskell version
  • Code builds on Linux, MacOS and Windows for ghc-8.10.7 and ghc-9.2.7
• The changelog section in the PR is updated to describe the change
• Self-reviewed the diff

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[carbolymer]

This should fix IntersectMBO/cardano-cli#135

[Jimbo4350]

Nice, far better that what I was thinking of.