WIP: feat: implement Lance filter+count pushdown optimization

[huleilei]

This commit implements filter+count joint pushdown optimization for Lance tables, significantly improving query performance for count queries with filter conditions.

Key changes:

• Enhanced push_down_aggregation.rs to support filter+count joint pushdown
• Improved lance_scan.py to handle filter+count operations natively
• Updated _lancedb_count_result_function to process filters correctly
• Enhanced test coverage for filter+count pushdown scenarios

The optimization maintains backward compatibility and includes graceful fallback mechanisms for unsupported filter expressions.

Changes Made

Related Issues

Checklist

• [ ] Documented in API Docs (if applicable)
• [ ] Documented in User Guide (if applicable)
• [ ] If adding a new documentation page, doc is added to docs/mkdocs.yml navigation
• [ ] Documentation builds and is formatted properly (tag @/ccmao1130 for docs review)

[codecov[bot]]

Codecov Report

:x: Patch coverage is 97.18310% with 4 lines in your changes missing coverage. Please review. :white_check_mark: Project coverage is 74.59%. Comparing base (1245eb5) to head (0e61b08). :warning: Report is 359 commits behind head on main.

Files with missing lines	Patch %	Lines
...an/src/optimization/rules/push_down_aggregation.rs	97.56%	3 Missing :warning:
daft/io/lance/lance_scan.py	92.30%	1 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #5152      +/-   ##
==========================================
+ Coverage   73.69%   74.59%   +0.90%     
==========================================
  Files         969      969              
  Lines      126099   124370    -1729     
==========================================
- Hits        92926    92777     -149     
+ Misses      33173    31593    -1580     

Files with missing lines	Coverage Δ
...rc/daft-logical-plan/src/optimization/optimizer.rs	94.00% <100.00%> (+0.82%)	:arrow_up:
src/daft-micropartition/src/python.rs	66.96% <100.00%> (+0.06%)	:arrow_up:
daft/io/lance/lance_scan.py	90.90% <92.30%> (+24.53%)	:arrow_up:
...an/src/optimization/rules/push_down_aggregation.rs	96.35% <97.56%> (+0.80%)	:arrow_up:

... and 31 files with indirect coverage changes

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[kevinzwang]

@huleilei instead of resubmitting the PR, I think if you ping @greptileai, Greptile will review your PR again

[huleilei]

@rchowell @kevinzwang @Jay-ju help me review when you are convenient. Thanks

[huleilei]

@kevinzwang Tests are passing, help me merge when you are convenient. Thanks

[kevinzwang]

Merged. Thank you!