refactor(rust): Fix simple projection in streaming engine

[orlp]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 8 lines in your changes missing coverage. Please review.

Project coverage is 80.47%. Comparing base (3016c07) to head (3dd2468).

Files	Patch %	Lines
...rates/polars-stream/src/nodes/simple_projection.rs	0.00%	6 Missing ⚠️
crates/polars-stream/src/physical_plan/lower_ir.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #17871      +/-   ##
==========================================
- Coverage   80.47%   80.47%   -0.01%     
==========================================
  Files        1505     1505              
  Lines      197273   197278       +5     
  Branches     2807     2807              
==========================================
- Hits       158764   158762       -2     
- Misses      37987    37994       +7     
  Partials      522      522              

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