Fix GROUP BY alias in subquery generation

[PrabhbirJ]

Description

Fixed invalid SQL generation in subquery GROUP BY clauses. The _resolve_group_bys method was incorrectly adding field aliases to GROUP BY clauses, causing invalid SQL syntax like GROUP BY "name" "alias" instead of the correct GROUP BY "name".

Motivation and Context

#1999
It fixes the open issue 1999.

How Has This Been Tested?

Added regression test test_subquery_group_by_no_alias to verify GROUP BY clauses don't include aliases
Ran make check - all style, lint, and tests passed
Verified SQL generation produces valid GROUP BY "field" instead of invalid GROUP BY "field" "alias"
Tested with the exact reproduction case from issue #1999

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added the changelog accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[codspeed-hq]

CodSpeed Performance Report

Merging #2001 will not alter performance

_{Comparing PrabhbirJ:fix-subquery-groupby-alias (08f74ba) with develop (f660db0)}

Summary

✅ 16 untouched