feat(python): Ensure AWS credential provider sources AWS_PROFILE from environment after deserialization

[nameexhaustion]

Intended for cloud / remote execution support.

It currently uses the one sourced during local initialization even after being deserialized on a remote machine.

Note that a case that we still don't handle well is if a user's local machine doesn't have permissions to the cloud storage, while the remote machine does. In this case remote execution will also not use a credential provider.

What I think should instead happen is that the _maybe_init_credential_provider() credential provider resolution is performed on the remote machine before the query is executed. Doing this is a bit more involved, but I plan to get this working next week.

[codecov]

Codecov Report

Attention: Patch coverage is 16.66667% with 5 lines in your changes missing coverage. Please review.

Project coverage is 79.29%. Comparing base (15fa50a) to head (c68a4f7).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
py-polars/polars/io/cloud/credential_provider.py	16.66%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #21121      +/-   ##
==========================================
- Coverage   79.29%   79.29%   -0.01%     
==========================================
  Files        1589     1589              
  Lines      226515   226515              
  Branches     2594     2594              
==========================================
- Hits       179611   179607       -4     
- Misses      46308    46312       +4     
  Partials      596      596              

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