[MCC-1535269] Python SDK - Remove dataset_batch_number from publish and dry_publish results

[dsilaghi-mdsol]

bug

• Python SDK - Remove dataset_batch_number from publish and dry_publish results
• MCC-1535269

Checklist

• Review the pull request to fix typos and ensure variable/function names are intuitive, etc.
• Make sure the pull request does not have excessive number of unnecessary commits. Utilize the git commit --amend --no-edit command to reduce commit messages when making small file changes (like changing linespacing).
• Make sure you have added unit tests for the code changes. Tests should be added in the tests/ folder.
• Modify docs, if required. Add any new documentation in the doc/ folder.
• Rebase on latest active development branch (develop/main).

Changes Summary

Remove dataset_batch_number from ResultMetadata and the _PublishEnvelopeResult flat accessor so the field is absent from both repr() and asdict() output, covering the QA validation path (json.dumps(asdict(result))).

• Drop dataset_batch_number field from ResultMetadata dataclass.
• Drop the flat dataset_batch_number property shim from _PublishEnvelopeResult.
• Stop mapping the field in _envelope_to_domain; transport/models.py is untouched (server still sends it, transport still parses it).
• Replace repr-based test assertions with asdict-based ones to match the actual QA evidence path.

Deployment Notes

result.dataset_batch_number and result.metadata.dataset_batch_number now raise AttributeError. Any callers reading the field directly will need to be updated.