Add post deployment migration to complete Pages metadata migration
What does this MR do?
There are no such jobs left on GitLab.com and we have 1 project that has no its data migrated (not sure why). The initial variant of this MR included the query to populate
project_pages_metadata for such projects but given the time it will take to run we decided not to do this and rely on the record being created/updated when Pages are deployed for these projects (e.g. https://gitlab.com/gitlab-org/gitlab/blob/9e7db9b1f4e0726874f4dabb9db1421cac736ce3/app/services/projects/update_pages_service.rb#L54-58). See !19928 (comment 254801462) for more details.
Related to #28781 (closed).
Does this MR meet the acceptance criteria?
- Changelog entry
- [-] Documentation (if required)
- Code review guidelines
- Merge request performance guidelines
- Style guides
- Database guides
- [-] Separation of EE specific content