Fix missing gov action on balance transaction

[palas]

Changelog

- description: |
    Fixed a bug that caused balancing algorithm to drop unwitnessed government actions
  type:
  - bugfix

Context

This PR:

• Fixes the bug reported in this issue: Governance actions silently stripped from transaction cardano-cli#1073
• Adds a regression test to warn us at the cardano-api level if such a problem occurs again

How to trust this PR

Check the test. You can verify that it fails if applied before the fix.
Check that the code style is correct, that the changes make sense, and the new code doesn't introduce any new bugs.

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

[carbolymer]

This changes the order of proposals: unwitnessed proposals are placed before witnessed ones. I am only aware about script indexing relying on the order (which should be ok after your change) but I don't know if it's not breaking any other hidden ledger invariants about proposals.

Let's be on the safer side and don't change the order of the proposals.