feat: Move diagonal & horizontal concat schema resolving to IR phase

[ritchie46]

This also make diagonal concat faster as we did mutliple with_columns sequentially. Now they are batched.

[ritchie46]

Removed this as a Schema cannot have multiple columns.

[codecov]

Codecov Report

Attention: Patch coverage is 96.25000% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 80.91%. Comparing base (222216a) to head (0f4f5ec).
Report is 2 commits behind head on main.

❗ Current head 0f4f5ec differs from pull request most recent head 92e48d0. Consider uploading reports for the commit 92e48d0 to get more accurate results

Files	Patch %	Lines
py-polars/src/lazyframe/visitor/nodes.rs	0.00%	2 Missing ⚠️
...-plan/src/logical_plan/conversion/convert_utils.rs	98.36%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16034   +/-   ##
=======================================
  Coverage   80.91%   80.91%           
=======================================
  Files        1385     1385           
  Lines      178244   178229   -15     
  Branches     3050     3050           
=======================================
- Hits       144229   144218   -11     
+ Misses      33526    33521    -5     
- Partials      489      490    +1     

Flag	Coverage Δ
python	74.39% <96.25%> (-0.01%)	⬇️
rust	78.13% <96.25%> (+<0.01%)	⬆️

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