PERF: Update some `User` associations` to dependent: :delete_all`. (PR #9789)

dependent: :destroy creates an AR object and then calls destroy on it which is slow. For certain associations, we do not run callbacks or need to run callbacks so we should avoid creating all the AR objects.

GitHub

I’ve look through the associations and these associations do not have any before or after destroy callbacks.

Nice change, thanks for auditing it!

Closed by https://github.com/discourse/discourse/commit/6b92c78033a1a26eea56f0417b6811581fab7a38