fix: allow search_sorted directly on multiple chunks, and fix behavior around nulls

[orlp]

Closes #16420.

[codecov]

Codecov Report

Attention: Patch coverage is 91.27517% with 13 lines in your changes are missing coverage. Please review.

Project coverage is 81.45%. Comparing base (462bc8b) to head (4355642).
Report is 11 commits behind head on main.

Files	Patch %	Lines
...polars-core/src/chunked_array/ops/search_sorted.rs	90.57%	13 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #16447      +/-   ##
==========================================
+ Coverage   81.43%   81.45%   +0.01%     
==========================================
  Files        1409     1409              
  Lines      184678   184730      +52     
  Branches     2971     2971              
==========================================
+ Hits       150396   150475      +79     
+ Misses      33762    33735      -27     
  Partials      520      520              

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[ritchie46]

@orlp can you do a doctest run?

[orlp]

@ritchie46 That test failure isn't really a failure, the default behavior is "any", and I just changed the default behavior of any to be equivalent to "left" (which is a valid return value for any). I'll update that test.