Fix selection size when canvas limits are set for Points

[brisvag]

References and relevant issues

Closes https://github.com/napari/napari/issues/6682

Description

The selection markers were not updated accordingly.

This is still not perfect (zooming in and out beyond the limits will change the thickness of the highlight), but it's a limitation of how hilight is implemented (by just using extra markers). Ideally we want to have a single marker take care of hilight as well, but this requires rewriting the shaders and it's not trivial.

[psobolewskiPhD]

Hmm, I don't see the donut effect anymore, but I also don't see the highlight at all. I changed thickness to 3 as well.

• New Pts layer, set scale (.1, .1)
• add some points, hit a to select all.
• mess with canvas_size_limits

Do the selection markers need to be canvas_size + highlight thickness?

[brisvag]

Good point... what about now?

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 92.39%. Comparing base (caf6caf) to head (e395597). Report is 15 commits behind head on main.

Files	Patch %	Lines
napari/_vispy/visuals/points.py	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #6853 +/- ## ========================================== - Coverage 92.44% 92.39% -0.05% ========================================== Files 614 614 Lines 54843 54859 +16 ========================================== - Hits 50697 50686 -11 - Misses 4146 4173 +27 ```

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[psobolewskiPhD]

The behavior seems good now. I did notice that the highlight scales with zoom differently than point size, but the same behavior happens on main.