Respect resolutions when copying segmentation slice

[philippotto]

For anisotropic datasets, copying a segmentation slice (via "v") in viewports other than xy didn't work properly. Some voxels outside the visible viewport were copied even though this should not be the case.

URL of deployed dev instance (used for testing):

• https://fixcopysegmentation.webknossos.xyz

Steps to test:

• brush over the edges in yz and xz viewport
• move to next slice
• hit "v"
• move the viewports to see that the brushed segmentation has a hard cut (--> only visible voxels were written)

Issues:

• fixes Copy segmentation slice copies data from outside the visible viewport for xz and yz #3243

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• Updated changelog
• Ready for review

[daniel-wer]

Nice find, tested and works!