Research and discussion: Provisioning Container Registry Database for Omnibus

Before implementing the Omnibus change, we'll need to develop a plan. Discussions have been happening in gitlab-org/quality/reference-architectures#246 and gitlab-org/distribution/team-tasks#606 but we don't have an actionable implementation path.

Objectives of this issue:

• Continue discussions and make a decision on how to begin the Omnibus implementation
• Break down Omnibus changes into iterative tasks for scheduling in subsequent milestones.