Allow Publishing AI Models to Paths/S3

[fm3]

Introduces a new protocol for publishing and accessing AI models. Similar to datasets, a path field is added in postgres, and the uploadToPaths prefix can be selected.

When using the model, the client can access the path via the API and then load the data from there.

The old register route for trained ai models was removed. When this upgrade is deplyoed, the corresponding new voxelytics version that uses the new publish model protocol must be used when training models.

Steps to test:

• Test publishing and accessing AI models via voxelytics.

TODOs:

• [x] add path to ai model
• [x] evolution
• [x] routes to reserve + finish upload
• [x] do we need a status field to differentiate between path set but not yet finished?
• [x] route to get path of aiModel

Corresponding PRs

• libs https://github.com/scalableminds/webknossos-libs/pull/1409
• voxelytics https://github.com/scalableminds/voxelytics/pull/4417

Issues:

• fixes #9033

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• [x] Added changelog entry (create a $PR_NUMBER.md file in unreleased_changes or use ./tools/create-changelog-entry.py)
• [x] Added migration guide entry if applicable (edit the same file as for the changelog)
• [x] Removed dev-only changes like prints and application.conf edits
• [x] Considered common edge cases