Bump rq, django-rq and sentry-sdk

Closes #1906 (closed), !2258, !2268 (merged), !2373

I was surprised by the complete lack of any breaking changes. It turns out django-rq (made by the same people as RQ) absorbs them all, solving almost everything.

I had a deeper look at the Sentry integration since the breaking changes do mention that. The errors were somehow no longer coming through, so I upgraded sentry-sdk to the latest version and got a test issue through.

I also tried to run a thousand useless jobs at once to reproduce the conditions that made us reimplement some of the inner workings of registries ourselves in ListJobs. We still do need this reimplementation, and it still works as it is. If we ever run into those issues once again somewhere else, we at least have a new cleanup=False option to disable the problematic cleanup.