server: Ensure we have distinct codeintel database
Created by: efritz
This PR closes https://github.com/sourcegraph/sourcegraph/issues/14464, which raises the concern about the upgrade path from server -> docker-compose/k8s. We don't want all of the lsif data to be crammed into the same database, as the upgrade instructions will be too much effort on a client (pg dump these tables and move them here, but these tables go here, etc). Instead, I'm just making another database along with the default sourcegraph one, which should simplify migrations off of server.
The server deployment should now be able to support
- One local instance, two databases both used by app
- One local instance, one database used by app + an external database
- Two external databases, no local instance