refactor(rust): Add streaming groupby for reductions

[orlp]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 28.47100% with 407 lines in your changes missing coverage. Please review.

Project coverage is 79.89%. Comparing base (dae6cd9) to head (9ff7a20).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-stream/src/nodes/group_by.rs	0.00%	138 Missing ⚠️
crates/polars-expr/src/groups/row_encoded.rs	0.00%	134 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 ⚠️
...-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 ⚠️
crates/polars-expr/src/reduce/convert.rs	0.00%	2 Missing ⚠️
... and 9 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19291      +/-   ##
==========================================
- Coverage   80.00%   79.89%   -0.12%     
==========================================
  Files        1528     1532       +4     
  Lines      209850   210239     +389     
  Branches     2419     2419              
==========================================
+ Hits       167894   167960      +66     
- Misses      41405    41728     +323     
  Partials      551      551              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.