refactor(python): Clean up some of the AnyValue conversion logic

[stinodego]

Mostly a lot of refactoring, but also addressed some minor issues.

[codecov]

Codecov Report

Attention: Patch coverage is 99.26740% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 81.23%. Comparing base (6a87324) to head (272ee1e).
Report is 2 commits behind head on main.

Files	Patch %	Lines
py-polars/polars/_utils/construction/dataframe.py	33.33%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #15190      +/-   ##
==========================================
+ Coverage   81.22%   81.23%   +0.01%     
==========================================
  Files        1348     1348              
  Lines      175330   175304      -26     
  Branches     2508     2509       +1     
==========================================
+ Hits       142409   142412       +3     
+ Misses      32442    32411      -31     
- Partials      479      481       +2     

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[stinodego]

Note: Constructing a Series with an uninstantiated pl.Array was and is still broken:

import polars as pl

s = pl.Series([[1, 2], [3, 4]], dtype=pl.Array)
print(s)
# ValueError: cannot construct PySeries for type Array