feat: add support for next_day expression

[andygrove]

Summary

• Adds native Comet support for Spark next_day function
• Returns the first date after a given start date that falls on the specified day of week
• Supports full day names (Sunday, Monday, etc.) and abbreviations (Sun, Mon, etc.)
• Invalid day names return NULL (matching Spark's non-ANSI mode behavior)

Test Plan

• Added unit tests in CometTemporalExpressionSuite
• Tests include all 7 days with full names and abbreviations
• Tests include literal dates and null handling
• All existing tests pass

Note: This PR was generated with AI assistance.

Closes #3092

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 59.87%. Comparing base (f09f8af) to head (990d16d).
⚠️ Report is 848 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3148      +/-   ##
============================================
+ Coverage     56.12%   59.87%   +3.74%     
- Complexity      976     1414     +438     
============================================
  Files           119      168      +49     
  Lines         11743    15587    +3844     
  Branches       2251     2589     +338     
============================================
+ Hits           6591     9332    +2741     
- Misses         4012     4946     +934     
- Partials       1140     1309     +169     

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[comphead]

Can we use next_day from DataFusion? https://github.com/apache/datafusion/blob/main/datafusion/spark/src/function/datetime/next_day.rs