Change a representation of witnesses in transaction's certificates to an ordered map where a certificate is the key

[carbolymer]

Changelog

- description: |
    Change a representation of witnesses in transaction's certificates to an ordered map where a certificate is the key.
# 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

This PR changes representation of transaction certificates' witnesses from a list of with stake credentials to a map.

The issue is that there's a relationship Certificate *--1 StakeCredential which makes the assigning of witnesses impossible in the cases where we have more than one certificate with the same stake credential. This then breaks witnesses indexing.

See related PRs:

• Fix costs calculation for transaction with more than one certificates with the same stake credential and script witness cardano-cli#1028
• cardano-testnet | Create transaction with two script certificates test cardano-node#6082

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]

Confirm we aren't reintroducing a bug and I'll be happy to approve.

[Jimbo4350]

This makes my eyes bleed (I know it's not your fault).

[Jimbo4350]

I would seek confirmation that #456 is not an issue with this change. I suspect this needs to be a list still.

[Jimbo4350]

I would add a ord_distributive test for Certificate just to be safe.