Draft: Skip post-deployment migrations for registry DB by default

What does this MR do?

This is the first step towards Container Registry: Implement methodology for p... (#3926). Builds on top of gitlab-org/build/CNG!1208 (merged).

While we don't have the automation to apply post-deployment migrations as we currently have for regular ones (#2566 (closed)), we'll need to at least be able to tell db-migrate/wait-for-deps scripts to ignore any non-applied post-deployment migrations included in new registry versions so that they are not applied during deployments. We'll then have to raise a production change request to have those post-deployment migrations applied manually from within a registry node.

Related issues

Related to #3926.

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
• When ready for review, MR is labeled "~workflow::ready for review" per the Distribution MR workflow

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
• Validate potential values for new configuration settings. Formats such as integer 10, duration 10s, URI scheme://user:passwd@host:port may require quotation or other special handling when rendered in a template and written to a configuration file.