Logistic Regression: Binary class labels getter

[DGPardo]

Expose a reference to the mapping from the ground truth data label to the assigned binary label used in the logistic regression model.

This goes in line with the output provided by MultiFittedLogisticRegression that has a method to access classes

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (0d8b62a) 36.73% compared to head (cf15ccd) 36.71%.

Files	Patch %	Lines
algorithms/linfa-logistic/src/lib.rs	0.00%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #325      +/-   ##
==========================================
- Coverage   36.73%   36.71%   -0.02%     
==========================================
  Files          94       94              
  Lines        6240     6242       +2     
==========================================
  Hits         2292     2292              
- Misses       3948     3950       +2     

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[quietlychris]

Since these methods/structs are being made public, can you add doc comments for each? Otherwise this looks good, although you may need to rebase onto master. The CI isn't passing right now bc of what looks like a Windows linking issue, but I'll don't think that should gate this being merged.

[DGPardo]

Thanks for your review @quietlychris
I think I have addressed your requests, otherwise please let me know

[quietlychris]

Looks good, thank you!