[REF] Do not modify mixing matrix with sign-flipping

[tsalo]

Closes #748.

Changes proposed in this pull request:

• Add new metric, "optimal sign", to component tables.
• Do not return sign-flipped mixing matrix from metrics.collect.generate_metrics().
• Write out unmodified mixing matrix in main workflow.
• Coerce signs to integers rather than floats. This will make the metric values in the component table easier to interpret.

[codecov]

Codecov Report

Merging #749 (48017e2) into main (d449925) will decrease coverage by 0.01%.
The diff coverage is 95.45%.

@@            Coverage Diff             @@
##             main     #749      +/-   ##
==========================================
- Coverage   92.61%   92.59%   -0.02%     
==========================================
  Files          27       27              
  Lines        2125     2121       -4     
==========================================
- Hits         1968     1964       -4     
  Misses        157      157              

Impacted Files	Coverage Δ
tedana/workflows/tedana.py	90.30% <87.50%> (-0.07%)	⬇️
tedana/decomposition/pca.py	86.51% <100.00%> (-0.15%)	⬇️
tedana/metrics/_utils.py	68.00% <100.00%> (+0.65%)	⬆️
tedana/metrics/collect.py	95.00% <100.00%> (-0.09%)	⬇️
tedana/reporting/static_figures.py	97.87% <100.00%> (+0.02%)	⬆️

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[jbteves]

This is a great refactor, thanks @tsalo ! Good job cleaning up the logic I had for ordering the table. However, I think it would be good to stick with our save_file interface. Either you can add something to add the component index or I can if you'd prefer.

[tsalo]

@jbteves thanks for reviewing. I think I was just overcomplicating the TSV saving procedure. If I just keep the "Component" ID column as a column instead of the index, it should be fine.

EDIT: Yup, as of 48017e2 it all looks good.

[jbteves]

LGTM, thanks so much @tsalo !

[eurunuela]

Changes look good to me. Thank you @tsalo ! I'll leave it to you to merge this PR.