Add a "Database Cluster Status" console in Config

Summary: Ref T4571. The configuration option still doesn't do anything, but add a status panel for basic setup monitoring.

Test Plan:
Here's what a good version looks like:

Also faked most of the errors it can detect and got helpful diagnostic messages like this:

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T4571

Differential Revision: https://secure.phabricator.com/D15667