perf(python): Make expensive selector expansion lazy

[ritchie46]

Will do a bunch of them.

[codecov]

Codecov Report

Attention: Patch coverage is 78.60697% with 43 lines in your changes missing coverage. Please review.

Project coverage is 80.33%. Comparing base (9dd9569) to head (170fbb3).
Report is 1 commits behind head on main.

Files	Patch %	Lines
py-polars/src/lazyframe/visitor/nodes.rs	0.00%	15 Missing ⚠️
crates/polars-plan/src/plans/functions/mod.rs	52.38%	10 Missing ⚠️
crates/polars-plan/src/plans/functions/dsl.rs	84.78%	7 Missing ⚠️
crates/polars-plan/src/plans/conversion/mod.rs	0.00%	5 Missing ⚠️
py-polars/polars/lazyframe/frame.py	80.00%	1 Missing and 1 partial ⚠️
...rs-lazy/src/physical_plan/streaming/convert_alp.rs	0.00%	1 Missing ⚠️
crates/polars-plan/src/client/check.rs	50.00%	1 Missing ⚠️
crates/polars-plan/src/dsl/options.rs	0.00%	1 Missing ⚠️
crates/polars-plan/src/plans/builder_ir.rs	75.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #18118   +/-   ##
=======================================
  Coverage   80.33%   80.33%           
=======================================
  Files        1496     1496           
  Lines      197685   197746   +61     
  Branches     2821     2822    +1     
=======================================
+ Hits       158806   158859   +53     
- Misses      38358    38365    +7     
- Partials      521      522    +1     

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[ritchie46]

@alexander-beedie I got almost all of them except for the one in lf.cast. Maybe we can translate the cast selectors to a with_columns(<selector>.cast()). That will automatically be resolved in the rust side.