feat: improve logging setup

[federicobond]

This PR

Replaces the root logger with a custom logger for all logs emitted by the package.

I believe this should cover the logging requirements for the SDK, since logs can be manipulated later via handlers and formatters using the standard library logging package interface.

Follow-up Tasks

• If we agree, mark this package as supporting logging configuration in the README.

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (15ce8f9) 93.84% compared to head (bab6c03) 93.89%.

Files	Patch %	Lines
openfeature/client.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #261      +/-   ##
==========================================
+ Coverage   93.84%   93.89%   +0.04%     
==========================================
  Files          16       16              
  Lines         439      442       +3     
==========================================
+ Hits          412      415       +3     
  Misses         27       27              

Flag	Coverage Δ
unittests	93.89% <75.00%> (+0.04%)	⬆️

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[gruebel]

👍