Expose symbols required by hash check in transaction build in cardano-cli

[palas]

Changelog

- description: |
    Exposed `GovAction` and `Constitution` types and constructors required by hash check in `transaction build` in `cardano-cli`
  type:
  - feature

Context

Work to check anchor data in transactions being build with transaction build command of
cardano-cli requires inspecting the GovAction and Constitution types, which are currently not exposed by cardano-api but by cardano-ledger-api (see branch hash-check-in cardano-cli ). In order to avoid transitive dependencies, this PR exposes the required types and constructors.

How to trust this PR

Tiny PR. I just would ensure it is right to export these, that they are not exported anywhere else, and that they are imported in the right way.

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