Switch CI to new metadata collection
r? `@xFrednet`
Things we have to keep in mind:
- This removes the template files and the scripts used for deployment from the checkout. This was added in #5517. I don't think we ever needed those there. Not sure though.
- ~~As a result, we can't remove the python scripts yet. We have to wait until this hits a stable Clippy release.~~ I'll just break the next stable deploy and do it by hand once.
- This should be merged together with #7279. Me and `@xFrednet` will coordinate the switch
- ...?
I still have to try out some things:
- [x] Is it worth caching? Yes
- [x] ~~Is it worth to do a release build?~~ Nope
- [x] Does it actually work? With a few changes, yes
- [ ] ...?
changelog: Clippy now uses a lint to generate its documentation 🎉
bcdf147aaf