Remove createPreviousGovernanceActionId. Use GovPurposeId directly instead.

[carbolymer]

Changelog

- description: |
    Removed `createPreviousGovernanceActionId`. Use `GovPurposeId . createGovernanceActionId` instead.
    Export `GovPurposeId` through `Cardano.Api.Ledger`.
# uncomment types applicable to the change:
  type:
  # - feature        # introduces a new feature
   - breaking       # the API has changed in a breaking way
  # - compatible     # the API has changed but is non-breaking
  # - optimisation   # measurable performance improvements
   - refactoring    # QoL changes
  # - bugfix         # fixes a defect
  # - test           # fixes/modifies tests
  # - maintenance    # not directly related to the code
  # - release        # related to a new release preparation
  # - documentation  # change in code docs, haddocks...

Context

Because the L.GovPurposeId no longer requires constraint EraCrypto (ShelleyLedgerEra era) ~ StandardCrypto it's easier to use the constructor directly, without extra type hints for compiler.

Changes in cardano-cli implemented in:

• Use GovActionId instead of tuples in commands cardano-cli#1119

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