Add extra functions to Cardano.Api.Tx.UTxO.

[locallycompact]

Changelog

- description: |
    Add `toMap` synonym for `unUTxO`, `resolveTxIn` synonym for `lookup` functions to `Cardano.Api.Tx.UTxO`.
# 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

We find the synonym toMap to be more appropriate than unUTxO to use qualified, as in UTxO.toMap. We also find resolveTxIn to be more appropriate than lookup as it is domain specific.

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