[FIX] PCA: ensure tests pass on sklearn 1.4 and 1.5, which can return different results

[pavlin-policar]

Issue

#6815 broke a few things that went under the radar, primarily due to scikit-learn 1.5.0 changes.

Includes

• Code changes
• Tests
• Documentation

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 88.26%. Comparing base (8831a57) to head (b9625da).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #6821      +/-   ##
==========================================
- Coverage   88.26%   88.26%   -0.01%     
==========================================
  Files         326      326              
  Lines       71156    71158       +2     
==========================================
+ Hits        62805    62806       +1     
- Misses       8351     8352       +1     

[pavlin-policar]

@markotoplak As far as I can tell, none of the remaining failures have anything to do with #6815. This should be good to merge.

[pavlin-policar]

For posterity's sake: PCA can produce different results between scikit-learn versions 1.4.0 and 1.5.0 in that the directions of the vectors may be flipped. While they do ensure a consistent output within each version of scikit-learn using their svd_flip function here, the u_based_decision was changed to False in 1.5.0, while it was True (the default) in prior versions of scikit-learn. Here is the commit that makes this change.

This change, which causes inconsitencies between scikit-learn 1.4.0 and 1.5.0 was not discussed in their PR, but it was apparently necessary to make the outputs of PCA consistent between the different solvers in 1.5.0 (original PR and comment here).