fix(optimizer): Take full expression nullability into account for join key nullability

[AdamGS]

Which issue does this PR close?

• Closes Nullable expression over non-null columns are planned as non-null-aware-joins #25024.

Rationale for this change

NOT IN can return incorrect results when expressions such as NULLIF produce NULL from non-nullable inputs. Anti joins can retain rows that should be excluded, while mark joins lose SQL UNKNOWN.

Nullable correlation expressions can also unnecessarily enable null-aware
execution when both membership values are non-nullable.

What changes are included in this PR?

Determine null-awareness from the full outer membership expression and projected inner value, using their respective input schemas. Correlation predicates do not contribute to membership nullability.

What is the testing strategy for this PR?

Added unit tests and SLT regressions tests that now pass

Are there any user-facing changes?

Some queries are now correct

[codecov-commenter]

Codecov Report

❌ Patch coverage is 82.11382% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 81.71%. Comparing base (6ab4ce6) to head (8e33157).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
...on/optimizer/src/decorrelate_predicate_subquery.rs	82.11%	7 Missing and 15 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #25029      +/-   ##
==========================================
- Coverage   81.72%   81.71%   -0.01%     
==========================================
  Files        1127     1127              
  Lines      416237   416254      +17     
  Branches   416237   416254      +17     
==========================================
+ Hits       340156   340157       +1     
- Misses      56092    56104      +12     
- Partials    19989    19993       +4     

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