drep id: support key hash

[smelc]

Changelog

- description: |
    drep id: support key hash as input
# 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

While we're still unsure whether we should use https://cips.cardano.org/cip/CIP-0105 or https://cips.cardano.org/cip/CIP-129, we know we have to extend drep id to support key hashes and scripts. This PR makes a small forward and implements the former.

Part of fixing #883

How to trust this PR

Observe that we honor the behavior tagged as deprecated in CIP-105 (our existing already follows this behavior flagged "deprecated", so we are being consistent here):

• The existing golden tests for drep id still pass: we didn't change the default behavior

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

[smelc]

cc @CarlosLopezDeLara because this is the improvement we found out together during our pair programming session of yesterday