[BUG] Partially qualified joins join a.x = y and join x = b.y

[universalmind303]

previously we only supported either fully qualified a.x = b.y or no qualifiers x = y. this PR fixes this so we can use any combination of fully and partially qualified:
so all of the following combinations are now supported.

• x = y
• x = b.y
• y = x
• y = a.x
• a.x = y
• a.x = b.y
• b.y = x
• b.y = a.x

[codspeed-hq]

CodSpeed Performance Report

Merging #3290 will degrade performances by 23.56%

_{Comparing universalmind303:partially-qualified-joins (a53da24) with main (4470192)}

Summary

❌ 1 regressions
✅ 16 untouched benchmarks

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

Benchmarks breakdown

	Benchmark	main	universalmind303:partially-qualified-joins	Change
❌	test_show[100 Small Files]	32 ms	41.9 ms	-23.56%

[codecov]

Codecov Report

Attention: Patch coverage is 84.74576% with 9 lines in your changes missing coverage. Please review.

Project coverage is 77.50%. Comparing base (0720ffc) to head (0dc0e1f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/daft-sql/src/planner.rs	84.74%	9 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3290   +/-   ##
=======================================
  Coverage   77.50%   77.50%           
=======================================
  Files         666      666           
  Lines       81326    81358   +32     
=======================================
+ Hits        63029    63059   +30     
- Misses      18297    18299    +2     

Files with missing lines	Coverage Δ
src/daft-sql/src/planner.rs	69.17% <84.74%> (+0.23%)	⬆️

... and 3 files with indirect coverage changes

[kevinzwang]

Looks good, just one small comment