Add migrations job for Container Registry

What does this MR do?

Adds a Job that will run Registry migrations, and a dependencies container to the Deployments to wait for those migrations to complete.

• A Job added to perform migrations
• Document that manual database provisioning will be needed for upgrades
• Document that migrations behaviors will need to operate from an operational service container, when automatic migrations are disabled.

Related issues

Closes #2566 (closed) Closes #2621 (closed)

Testing configuration

examples/registry/databse-defaults.yaml

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion.

Required

• Merge Request Title and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Tests added
• Integration tests added to GitLab QA
• Equivalent MR/issue for omnibus-gitlab opened

Closes #2566 (closed)