feat: Convert concat during IR conversion

[ritchie46]

Still a few to go.

[codecov]

Codecov Report

Attention: Patch coverage is 89.83051% with 6 lines in your changes are missing coverage. Please review.

Project coverage is 80.91%. Comparing base (f03e7e0) to head (2c78e47).

Files	Patch %	Lines
crates/polars-plan/src/logical_plan/tree_format.rs	0.00%	5 Missing ⚠️
...lars-plan/src/logical_plan/conversion/dsl_to_ir.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16016      +/-   ##
==========================================
- Coverage   80.91%   80.91%   -0.01%     
==========================================
  Files        1384     1385       +1     
  Lines      178226   178225       -1     
  Branches     3050     3050              
==========================================
- Hits       144218   144210       -8     
- Misses      33519    33527       +8     
+ Partials      489      488       -1     

Flag	Coverage Δ
python	74.39% <89.83%> (+<0.01%)	⬆️
rust	78.13% <89.83%> (-0.01%)	⬇️

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