feat: Add maintain_order parameter to joins

[stijnherfst]

The API docs specify the ordering for left joins as preserving the order of the left Dataframe. In some cases it can be useful to also have this property for other types of joins and in other cases having no required ordering can allow for performance optimizations.

[codecov]

Codecov Report

Attention: Patch coverage is 89.88764% with 9 lines in your changes missing coverage. Please review.

Project coverage is 79.52%. Comparing base (0b1d520) to head (05aed8c).
Report is 21 commits behind head on main.

Files with missing lines	Patch %	Lines
crates/polars-python/src/conversion/mod.rs	53.84%	6 Missing ⚠️
crates/polars-ops/src/frame/join/mod.rs	96.66%	2 Missing ⚠️
crates/polars-ops/src/frame/join/args.rs	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #20026      +/-   ##
==========================================
+ Coverage   79.49%   79.52%   +0.02%     
==========================================
  Files        1556     1563       +7     
  Lines      216407   217248     +841     
  Branches     2456     2461       +5     
==========================================
+ Hits       172043   172776     +733     
- Misses      43806    43913     +107     
- Partials      558      559       +1     

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