feat: add support for array_position expression

[andygrove]

Summary

• Adds native Comet support for Spark's array_position function
• Returns the 1-based position of an element in an array, or 0 if not found

Implementation Details

This required a custom Rust implementation because DataFusion's array_position returns UInt64 and null when not found, while Spark returns Int64 (LongType) and 0.

Key implementation details:

• Returns Int64 to match Spark's LongType
• Returns 0 when element is not found (Spark behavior)
• Returns null when array is null or search element is null
• Supports both List and LargeList array types

Test Plan

• Added unit tests for array_position in CometArrayExpressionSuite
• Tests cover:
  • Finding elements in integer arrays
  • Finding elements in string arrays
  • Element not found (returns 0)
  • Arrays with null elements
  • Column-based queries (not just literals)
• All existing tests pass

Note: This PR was generated with AI assistance.

Closes #3153

[codecov-commenter]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 59.88%. Comparing base (f09f8af) to head (8cb27ec).
⚠️ Report is 849 commits behind head on main.

Files with missing lines	Patch %	Lines
...src/main/scala/org/apache/comet/serde/arrays.scala	75.00%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #3172      +/-   ##
============================================
+ Coverage     56.12%   59.88%   +3.75%     
- Complexity      976     1414     +438     
============================================
  Files           119      168      +49     
  Lines         11743    15598    +3855     
  Branches       2251     2591     +340     
============================================
+ Hits           6591     9341    +2750     
- Misses         4012     4948     +936     
- Partials       1140     1309     +169     

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