Use repository moving as way to undo joining object pool

For sanity, we want to have a way to roll back a repository joining a pool. #1548 (closed).

As a stopgap measure until we have a proper way to do this, we think it will work if you change the repository storage of the repo involved. This issue is to keep notes on verifying that it actually works like that.

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This is blocked by the fact that we have bugs in UpdateRepositoryStorageService and UnlinkRepositoryFromObjectPool that cause data loss. I'm using this issue to track resolving that bug now.