refactor(rust): Add streaming groupby for reductions

[orlp]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 27.55102% with 426 lines in your changes missing coverage. Please review.

Project coverage is 80.03%. Comparing base (c8aac32) to head (dde43a9).
Report is 44 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-stream/src/nodes/group_by.rs	0.00%	139 Missing ⚠️
crates/polars-expr/src/groups/row_encoded.rs	0.00%	135 Missing ⚠️
crates/polars-core/src/series/mod.rs	0.00%	46 Missing ⚠️
crates/polars-stream/src/physical_plan/lower_ir.rs	0.00%	25 Missing ⚠️
crates/polars-core/src/datatypes/dtype.rs	0.00%	17 Missing ⚠️
crates/polars-core/src/frame/mod.rs	0.00%	17 Missing ⚠️
...-core/src/chunked_array/logical/categorical/mod.rs	0.00%	10 Missing ⚠️
crates/polars-expr/src/groups/mod.rs	0.00%	10 Missing ⚠️
...es/polars-core/src/chunked_array/ops/row_encode.rs	94.54%	9 Missing ⚠️
crates/polars-core/src/schema.rs	0.00%	5 Missing ⚠️
... and 10 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19291      +/-   ##
==========================================
- Coverage   80.19%   80.03%   -0.17%     
==========================================
  Files        1527     1532       +5     
  Lines      210286   210708     +422     
  Branches     2440     2440              
==========================================
- Hits       168648   168635      -13     
- Misses      41083    41518     +435     
  Partials      555      555              

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