Draft: Migrate PostgreSQL-related services to Ruby

What does this merge request do and why?

Migrate PostgreSQL-related services to Ruby

This MR removes the various PostgreSQL instances and PgBouncer from the Procfile. It also adds more test coverage to the existing services and refactors them to allow for multiple replicas while ensuring backwards-compatibility with existing configuration.

How to set up and validate locally

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This MR references an issue describing the change.
• This change is backward compatible. If not, include steps to communicate to users.
• Tests added for new functionality. If not, raise an issue to follow-up.
• Observability added/updated (logging, metrics, tracing).
• Documentation added/updated.
• Announcement added for notable changes.
• gdk doctor test added.