fix: Run filter null join key optimization once

[colin-ho]

Only run the filter null join key optimization once before filter pushdown, instead of 3 times together with the other rules, otherwise you end up with something like [not(is_null(key)) & not(is_null(key))] & not(is_null(key)).

[codspeed-hq]

CodSpeed Performance Report

Merging #3657 will degrade performances by 33.32%

_{Comparing colin/filter-null-join-key-once (f94058b) with main (e0a2f69)}

Summary

⚡ 2 improvements
❌ 1 regressions
✅ 24 untouched benchmarks

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	main	colin/filter-null-join-key-once	Change
❌	test_iter_rows_first_row[100 Small Files]	129.4 ms	194.1 ms	-33.32%
⚡	test_show[100 Small Files]	23.8 ms	15.8 ms	+50.64%
⚡	test_tpch_sql[1-in-memory-native-8]	197.3 ms	156.1 ms	+26.38%

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.08%. Comparing base (426ddd0) to head (f94058b).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3657      +/-   ##
==========================================
+ Coverage   78.04%   78.08%   +0.04%     
==========================================
  Files         727      728       +1     
  Lines       89762    90092     +330     
==========================================
+ Hits        70052    70352     +300     
- Misses      19710    19740      +30     

Files with missing lines	Coverage Δ
...rc/daft-logical-plan/src/optimization/optimizer.rs	94.97% <100.00%> (+0.06%)	⬆️

... and 3 files with indirect coverage changes

[kevinzwang]

LGTM