test(python): Reorganize tests for clear operation

[stinodego]

Ref #15303

Added a test for #15303 and skipped it for now, as I didn't see an immediate solution to efficiently get the first non-null AnyValue value out of an Object Series.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.34%. Comparing base (9f1b08f) to head (0a1b748).
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #15304   +/-   ##
=======================================
  Coverage   81.34%   81.34%           
=======================================
  Files        1364     1364           
  Lines      176614   176614           
  Branches     2526     2526           
=======================================
+ Hits       143671   143672    +1     
  Misses      32459    32459           
+ Partials      484      483    -1     

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