refactor(python): Create NumPy view for Datetime/Duration Series on the Rust side

[stinodego]

Ref #14334

Changes

• Update the create_borrowed_np_array util to take a dtype parameter with the desired numpy dtype.
• Add support for views on Datetime/Duration Series (and remove the workaround on the Python side).

Some more work required to also support views on DataFrames with datetime/duration types, will do in another PR.

[codecov]

Codecov Report

Attention: Patch coverage is 97.87234% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 80.96%. Comparing base (c4e8678) to head (c577af3).
Report is 2 commits behind head on main.

Files	Patch %	Lines
py-polars/src/to_numpy.rs	97.82%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #16148   +/-   ##
=======================================
  Coverage   80.96%   80.96%           
=======================================
  Files        1386     1386           
  Lines      178437   178520   +83     
  Branches     2882     2881    -1     
=======================================
+ Hits       144463   144536   +73     
- Misses      33480    33491   +11     
+ Partials      494      493    -1     

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