Revert "query protocol parameters: use ledger instances"

[carbolymer]

This reverts commit 450a0a6.

This reverts #455 which breaks round-tripping of protocol parameters.

Fixes #472 & #474

Changelog

- description: |
    Revert #455 - use custom serialization for protocol parameters.
# uncomment types applicable to the change:
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  # - 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
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