Convert to wkw unit support

[MichaelBuessemeyer]

WK part to enable passing the user-provided unit to the wkw conversion job.

Please note that I tried to improve the typing and naming of the upload view in the frontend :). This just slipped in as an improvement.

URL of deployed dev instance (used for testing):

• https://___.webknossos.xyz

Steps to test:

• Better test locally in conjunction with the new worker pr #3666
• Set up a work with the version of the linked vx pr. (yarn enable-jobs)
• Upload a dataset that needs to be converted and select a unit other than nm
• After the upload and conversion are finished try viewing the dataset and check that the unit is according to what you configured during the upload.

Issues:

• fixes #7940

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(Please delete unneeded items, merge only when none are left open)

• Updated changelog

[fm3]

Backend LGTM, and works for me :) Just see my comment on parameter naming at https://github.com/scalableminds/voxelytics/pull/3666#discussion_r1703688121 which should also be applied here.

[MichaelBuessemeyer]

And while reviewing please use Hide whitespace. Else far to many changes are shown

[philippotto]

front-end lgtm :)