Preserve ordering equivalencies on with_reorder

[gokselk]

Which issue does this PR close?

Closes #13769.

Rationale for this change

The current implementation of with_reorder discards all existing ordering information when applying a new ordering. This is overly conservative since in many cases, parts of the existing ordering remain valid and could be preserved. Preserving valid orderings is important for query optimization as it allows the optimizer to avoid unnecessary sorting operations.

What changes are included in this PR?

1. Enhanced with_reorder() to preserve valid suffixes from existing orderings when they don't conflict with the new ordering
2. Added filtering of constant expressions from ordering considerations
3. Added exprs_equal() helper method to EquivalenceGroup for comparing expressions considering equivalence classes
4. Added comprehensive test suite covering:
   • Constant expression filtering
   • Suffix preservation
   • Equivalent expression handling
   • Incompatible prefix cases
   • Complex scenarios combining multiple features

Are these changes tested?

Yes, the PR includes extensive test coverage:

• test_with_reorder_constant_filtering: Tests filtering of constant expressions
• test_with_reorder_preserve_suffix: Verifies preservation of valid ordering suffixes
• test_with_reorder_equivalent_expressions: Tests handling of equivalent expressions
• test_with_reorder_incompatible_prefix: Ensures proper handling of incompatible orderings
• test_with_reorder_comprehensive: Tests complex interactions between constants, equivalences, and multiple orderings

Are there any user-facing changes?

This change is an internal optimization that preserves more ordering information. While there are no direct API changes, users may notice improved query performance in scenarios where ordering information is better preserved through operations that modify sort orders.

[gokselk]

cc: @berkaysynnada @ozankabak

[berkaysynnada]

LGTM