Add tests for v3 SQL generation edge cases

[shangyian]

Summary

This PR adds various tests around v3 SQL gen edge cases:

• Set-operation transforms: a transform whose body has UNION ALL does not support filter-pushdown today.
• Added test cases for various transform-query shapes (verifies the shape survives CTE building intact):
  • Derived table in FROM like (FROM (SELECT …)
  • A projected window function (ROW_NUMBER() OVER (…) AS rn)
  • A self-join with multi-condition on clause.
• Multi-filter composition into one CTE: two filters on the same parent (one via FK-rename, one via a qualified local column) both push into the parent's WHERE without duplication or drop.
• Three-level metric composition: C = B + A where B is itself derived from two base metrics. The resolution walks all three levels and inlines the full expansion.
• COALESCE in dimension-link join_sql: both FK columns stay in the parent CTE's projection so the JOIN can evaluate the COALESCE.
• Duplicate output aliases in a transform: pins the current silent-accept behavior as xfail which will be fixed with unifying validation across the single-node and bulk deployment methods.

Test Plan

• PR has an associated issue: #
• make check passes
• make test shows 100% unit test coverage

Deployment Plan

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