refactor(rust): Dispatch slice/filter lowering properly

[orlp]

This centralizes a remaining todo!() on the slice for negative slices, and fixed a non-streaming predicate bug in one instance (wasn't translated) and a todo!() in another case.

[codspeed-hq]

CodSpeed Performance Report

Merging #20390 will improve performances by 26.99%

_{Comparing orlp:lower-ir-refactor (f0ea4f6) with main (2c9e503)}

Summary

⚡ 1 improvements
✅ 40 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	orlp:lower-ir-refactor	Change
⚡	test_pdsh_q18	15.9 ms	12.5 ms	+26.99%

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 38 lines in your changes missing coverage. Please review.

Project coverage is 78.89%. Comparing base (db1684d) to head (f0ea4f6).
Report is 25 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-stream/src/physical_plan/lower_ir.rs	0.00%	38 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20390      +/-   ##
==========================================
- Coverage   79.10%   78.89%   -0.21%     
==========================================
  Files        1572     1567       -5     
  Lines      219958   219960       +2     
  Branches     2465     2465              
==========================================
- Hits       173991   173542     -449     
- Misses      45399    45850     +451     
  Partials      568      568              

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