Support distinct-from predicates in Parquet pruning

[Dandandan]

Which issue does this PR close?

• Closes #.

Rationale for this change

Parquet statistics pruning did not rewrite IS DISTINCT FROM or IS NOT DISTINCT FROM, so row groups that could be proven irrelevant from min/max and null-count statistics were still kept.

What changes are included in this PR?

• Adds null-aware pruning rewrites for IS DISTINCT FROM and IS NOT DISTINCT FROM.
• Treats distinct-from operators as symmetric when normalizing scalar-left predicates.
• Refactors shared min/max and null-count pruning expression builders.
• Adds unit tests for pruning predicate evaluation and Parquet row-group regression coverage.

Are these changes tested?

Are there any user-facing changes?

No API changes. Queries using IS DISTINCT FROM and IS NOT DISTINCT FROM can now benefit from Parquet statistics pruning.