Auto-delete projects of banned users after 60 days

What does this MR do and why?

Related to https://gitlab.com/gitlab-org/modelops/anti-abuse/team-tasks/-/issues/702

This MR adds workers that automatically delete projects created and owned by banned users after a 60-day waiting period.

References

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Enable the feature flag

   Feature.enable(:delete_banned_user_projects)

2. Create a user.
3. With the user create a project.
4. Invite the user as an owner of a project the user did not create.
5. Ban the user
6. Monitor the sidekiq and application logs

   tail -f log/sidekiq.log | grep BannedUserProjectDeletion
   tail -f log/application_json.log | grep BannedUserProjectDeletion

7. Trigger the AntiAbuse::BannedUserProjectDeletionCronWorker

   AntiAbuse::BannedUserProjectDeletionCronWorker.new.perform

8. Nothing should have happened since the user has not been banned for 60 days. Update the created_at timestamp of the banned user and re-trigger the worker. You should now see logs emitted related to the project deletion and the project created by the banned user should be destroyed.

   Users::BannedUser.last.update!(created_at: 61.days.ago)
   AntiAbuse::BannedUserProjectDeletionCronWorker.new.perform