mail_room was configured to deliver mail to the `incoming_email`
queue while `EmailReceiveWorker` was reading the `email_receiver`
queue. Adds a migration that repeats the work of a previous
migration to ensure all mails that wound up in the old
queue get processed.

Closes #23689

Dumping too many jobs in the same queue (e.g. the "default" queue) is a
dangerous setup. Jobs that take a long time to process can effectively
block any other work from being performed given there are enough of
these jobs.

Furthermore it becomes harder to monitor the jobs as a single queue
could contain jobs for different workers. In such a setup the only
reliable way of getting counts per job is to iterate over all jobs in a
queue, which is a rather time consuming process.

By using separate queues for various workers we have better control over
throughput, we can add weight to queues, and we can monitor queues
better. Some workers still use the same queue whenever their work is
related. For example, the various CI pipeline workers use the same
"pipeline" queue.

This commit includes a Rails migration that moves Sidekiq jobs from the
old queues to the new ones. This migration also takes care of doing the
inverse if ever needed. This does require downtime as otherwise new jobs
could be scheduled in the old queues after this migration completes.

This commit also includes an RSpec test that blacklists the use of the
"default" queue and ensures cron workers use the "cronjob" queue.

Fixes gitlab-org/gitlab-ce#23370

Fix project member access levels

Migrate invalid project members (owner -> master)

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/18616

See merge request !6957

The previous implementation of the migration failed on staging because
the migration was attempted to remove labels from projects that did not
actually have duplicates. This occurred because the SQL query did not
account for the project ID when selecting the labels.

To replicate the problem:

1. Disable the uniqueness validation in app/models/label.rb.
2. Create a duplicate label "bug" in project A.
3. Create the same label in project B with label "bug".

The migration will attempt to remove the label in B even if there are no duplicates.

Closes #23609