Unify segementation and color layers

[MichaelBuessemeyer]

This PR unifies the UI and its behaviour of segmentation and color layers in the dataset settings.

URL of deployed dev instance (used for testing):

• https://unifysegementationandcolorlayers.webknossos.xyz

Steps to test:

• open any dataset and check the following for a color layer and the segmentation layer:
  • the switch button should disable and hide the settings. It should also make the layer invisible in the viewports.
  • all options should work as before (e.g. the opacity option)
  • the color layer should have the color option, the segmentation layer should not.
  • the segmentation layer should additionally have the option "Highlight Hovered Cells".
  • both layers should have their name and element class at the top of their section in the settings.
  • the find data button should work for all layers
    edit: not for segmentations layers

Issues:

• fixes Unify handling of segmentation and color layer in settings #4044

---

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

[MichaelBuessemeyer]

@philippotto This PR is ready for your review. Please tell me what you think of my way of realizing this problem and how to maybe simplify the solution :)

[MichaelBuessemeyer]

@philippotto Could you please review this PR?
Please note that "find my data" is not working for segmentation layers as issue #4204 is still in my todo list :)

[philippotto]

Nice stuff! 🍬 See my few comments for feedback :)