Improve handling of movements in 3rd dimension

[philippotto]

This PR removes the old "clamp to edge" behavior on initial third-dimension movements, since this had undesired side effects (such as #5233). As a replacement, the keyboard delay is adapted according to the current position. See code comments for more details.

URL of deployed dev instance (used for testing):

https://fixvisiblemove.webknossos.xyz

Steps to test:

• open a dataset (ideally with a real-world scale, such as 11,11,24)
• turn down the move value to something unbearably slow (e.g., 5 nm/s which I allowed temporarily for this PR)
• play around with the position field (which now supports floats in this PR <-- I will undo this)
  • set the z-value to x.99 and move forward with f (keep the key pressed)
  • set the z-value to x.00 and move forward with f (keep the key pressed)
  • the experienced keyboard delay for the first scenario should be higher than for the second. you can also check the console output to see the calculated delays.

Issues:

• fixes Toggling between two slices does not visibly move other viewports #5233
• hopefully softens Nodes are shown in wrong slice when moving back and forth with low clipping distance #5653

---

• Updated (unreleased) changelog
• Updated (unreleased) migration guide if applicable
• Updated documentation if applicable
• Adapted wk-connect if datastore API changes
• Needs datastore update after deployment
• Ready for review

[philippotto]

Suggested change

	// todo: remove
	console.log({ moveDistanceIn1Second, passedFraction });

[philippotto]

@fm3 Feel free to check out https://fixvisiblemove.webknossos.xyz to see whether it's an improvement with regard to #5233.

[fm3]

Thanks! Yes, my use case is handled better now :)

[daniel-wer]

Very nice, feels exactly right now :)

LGTM once the temporary changes are reversed 👍