perf: Specialize first/last agg for simple types in new-streaming engine

[orlp]

Ensures we don't use the generic AnyValue path for numeric/temporal types, string types and bools.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 162 lines in your changes missing coverage. Please review.

Project coverage is 79.71%. Comparing base (e3216b4) to head (543da92).
Report is 5 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-expr/src/reduce/first_last.rs	0.00%	131 Missing ⚠️
crates/polars-expr/src/reduce/mod.rs	0.00%	15 Missing ⚠️
crates/polars-expr/src/reduce/min_max.rs	0.00%	8 Missing ⚠️
crates/polars-expr/src/reduce/mean.rs	0.00%	4 Missing ⚠️
crates/polars-expr/src/reduce/var_std.rs	0.00%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20728      +/-   ##
==========================================
- Coverage   79.75%   79.71%   -0.04%     
==========================================
  Files        1561     1561              
  Lines      221687   221914     +227     
  Branches     2530     2530              
==========================================
+ Hits       176796   176890      +94     
- Misses      44309    44442     +133     
  Partials      582      582              

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