refactor: Migrate polars-expr AggregationContext to use Column

[coastalwhite]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 82.28438% with 76 lines in your changes missing coverage. Please review.

Project coverage is 79.72%. Comparing base (3cdb7c2) to head (01a4266).
Report is 27 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-core/src/frame/column/mod.rs	78.12%	21 Missing ⚠️
crates/polars-core/src/frame/column/series.rs	67.74%	10 Missing ⚠️
crates/polars-expr/src/expressions/mod.rs	83.33%	10 Missing ⚠️
crates/polars-core/src/frame/mod.rs	11.11%	8 Missing ⚠️
crates/polars-core/src/scalar/mod.rs	0.00%	6 Missing ⚠️
crates/polars-expr/src/expressions/apply.rs	82.14%	5 Missing ⚠️
crates/polars-core/src/frame/column/scalar.rs	0.00%	4 Missing ⚠️
crates/polars-expr/src/expressions/aggregation.rs	95.23%	3 Missing ⚠️
crates/polars-expr/src/expressions/column.rs	78.57%	3 Missing ⚠️
crates/polars-expr/src/expressions/group_iter.rs	85.71%	2 Missing ⚠️
... and 4 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19736      +/-   ##
==========================================
- Coverage   79.73%   79.72%   -0.01%     
==========================================
  Files        1542     1544       +2     
  Lines      212223   212846     +623     
  Branches     2449     2441       -8     
==========================================
+ Hits       169216   169693     +477     
- Misses      42453    42604     +151     
+ Partials      554      549       -5     

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