R1:00bb0c907147

Raise setup warnings immediately when failing to load configuration from the database

Summary:
Ref T11589. Previously, when we failed to load database configuration we just continued anyway, in order to get to setup checks so we could raise a better error.

There was a small chance that this could lead to pages running in a broken state, where ONLY that connection failed and everything else worked. This was accidentally fixed by narrowing the exceptions we continue on in D16489.

However, this "fix" meant…