feat: Support descendingly-sorted values in search_sorted()

[itamarst]

Fixes #22821

Split out of #22633

[codecov]

Codecov Report

Attention: Patch coverage is 93.33333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 80.69%. Comparing base (d9195d5) to head (1fcedd2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
.../polars-python/src/lazyframe/visitor/expr_nodes.rs	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #22825      +/-   ##
==========================================
- Coverage   80.69%   80.69%   -0.01%     
==========================================
  Files        1671     1671              
  Lines      221268   221284      +16     
  Branches     2791     2791              
==========================================
+ Hits       178551   178560       +9     
- Misses      42052    42059       +7     
  Partials      665      665              

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[coastalwhite]

We should wait with this until the release is out.