Resolve "Admin dashboard: Show CI database name, and version"

What does this MR do and why?

The Instance Overview page (/admin page) shows the current PostgreSQL version. Gitlab supports running on two different databases. This MR will show the PostgreSQL versions for both configured databases.

Screenshots or screen recordings

Before:

After: (with one database)

After: (two databases)

How to set up and validate locally

View page /admin

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #346696 (closed)