Remove `deployed` column from `project_pages_metadata` and use `deployment_id` instead

This is complex, probably we'll need to break this issue to many smaller once.

When we migrate pages to new zip architecture we actually use deployed flag. So it may be wise to do this only in 15.0

• Start using deployment_id instead of deployed
• Verify pages API performance and create necessary indexes
• Remove this select: https://gitlab.com/gitlab-org/gitlab/-/blob/468b221d218c0689271088d8a7b8bbeea5639c5c/app/models/pages/virtual_domain.rb#L27