Keep coordinates in pixel units

[AnniekStok]

Scale world coordinates to pixel coordinates when exporting to geff, and scale back at import to align with the geff spec, as a potential solution for #261

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.84%. Comparing base (d9d83ea) to head (b229feb).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #262      +/-   ##
==========================================
- Coverage   93.86%   93.84%   -0.02%     
==========================================
  Files          59       59              
  Lines        3358     3398      +40     
==========================================
+ Hits         3152     3189      +37     
- Misses        206      209       +3     

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[cmalinmayor]

Design decision: segmentation shape and voxel size should be stored in tracksdata for in-graph segmentations, and thus saved in the geff. External segmentations should have the same metadata in their appropriate file format standards.

Aciton item for now: Always show the scale widget pre-filled with whatever metadata is present, and let the user change it during import if needed. Might need a slight hack for our internal save/load to ignore the scale for now.

Ideally, later: we should save in world coordiantes (no axis scales), and save the segmentation metadata in tracksdata (blocked by this not existing in tracksdata for voxel size yet).

[AnniekStok]

As per our final decision in #261, this is now keeping the coordinates in pixel units.
All regionprops features are scaled by tracks.scale.
Technically the centroid is also a regionprops feature, but it is now the only one that is not scaled. The scaling is applied in motile tracker when passing the locations to the solver and in the tree view and table view.
To not lose the scaling information, it is exported as columns in the CSV file. If we want we can also try to prefill the scaling when we import by looking for those column names.

I did not update the tests_old, so the tests are still expected to fail.

[TeunHuijben]

Once we agree to merge this, we should wait for #267, which makes this PR easier