refactor(rust): Group arguments in conversion in a Context

[ritchie46]

This is preparation for a fix where we set CSE in eager if we apply expression expansion. This is required as those expressions look stateful in the API, whilst it actually is syntactic sugar for multiple expressions. CSE will hide the symptoms here and align with expectation (except for random).

[codecov]

Codecov Report

Attention: Patch coverage is 84.09091% with 21 lines in your changes missing coverage. Please review.

Project coverage is 79.90%. Comparing base (22a97bf) to head (1189967).
Report is 52 commits behind head on main.

Files with missing lines	Patch %	Lines
...ates/polars-plan/src/plans/conversion/dsl_to_ir.rs	72.22%	10 Missing ⚠️
crates/polars-plan/src/plans/mod.rs	0.00%	6 Missing ⚠️
crates/polars-lazy/src/frame/mod.rs	84.84%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #18418      +/-   ##
==========================================
- Coverage   79.91%   79.90%   -0.01%     
==========================================
  Files        1495     1495              
  Lines      200261   200277      +16     
  Branches     2867     2867              
==========================================
+ Hits       160034   160038       +4     
- Misses      39681    39693      +12     
  Partials      546      546              

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