Extended to non-extended key: write description field in all cases

[smelc]

Changelog

- description: |
    Extended to non-extended key: write description field in all cases
# 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
  - improvement    # QoL changes e.g. refactoring
  # - 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

• Follow-up of key non-extended-key: support drep extended keys #377 (comment)
• Fixes Write descriptions in out files when generating non-extended keys, for all kinds of supported keys #413

How to trust this PR

Highlight important bits of the PR that will make the review faster. If there are commands the reviewer can run to observe the new behavior, describe them.

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

[Jimbo4350]

One comment that needs addressing: #416 (comment)

[smelc]

One comment that needs addressing: #416 (comment)

@Jimbo4350> since I addressed your comment, I'm enqueueing for merge.