feat: Delay deserialization of python function until physical plan

[ritchie46]

No description provided.

[codecov]

Codecov Report

Attention: Patch coverage is 75.00000% with 14 lines in your changes missing coverage. Please review.

Project coverage is 79.76%. Comparing base (b1b322f) to head (e1ed3b7).
Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-plan/src/dsl/expr.rs	47.61%	11 Missing ⚠️
crates/polars-plan/src/dsl/mod.rs	77.77%	2 Missing ⚠️
crates/polars-plan/src/dsl/expr_dyn_fn.rs	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #19069      +/-   ##
==========================================
+ Coverage   79.75%   79.76%   +0.01%     
==========================================
  Files        1531     1531              
  Lines      208547   208521      -26     
  Branches     2913     2913              
==========================================
+ Hits       166319   166330      +11     
+ Misses      41677    41640      -37     
  Partials      551      551              

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