feat: stateless logout

[alnr]

Closes #3836

Completely eliminates database writes during logout, except session deletion. We can drop table hydra_oauth2_logout_request completely -- I didn't in this PR tho.

There now is no more reuse detection for logout verifiers. But double-submit use cases work as before, so I don't think there is a observable or at least no meaningful difference in behavior.

Deleted a bunch of tests, too 🥰 🔥