Enable manual specification of execution units for plutus voting and proposing scripts

[Jimbo4350]

Changelog

- description: |
    Enable manual specification of execution units for plutus voting and proposing scripts
# 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...

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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]

Looks good 👍. One thing to consider is if we want --vote-execution-units to be optional. Making it optional would make it retro-compatible and more flexible.

It has to be manually specified in build-estimate. Making it optional would make it impossible to make a valid tx with a plutus voting script.