Remove "resolutions" from json dataset info route, adapt frontend and libs

[fm3]

For backwards compatibility, the StaticLayer writes currently appends "resolutions". However, this information could also be completely be taken from "mags" by the frontend.

The libs already use the new "mags" in scalableminds/webknossos-libs#1359

Once the frontend is adapted, we can remove the "resolutions" field completely.

This is a follow-up for #8844