Support loading config from flowfuse.yml in preference to flowforge.yml

### Description

Remove one of the last flowforge based configuration option

We should still support `flowforge.yml` (and `flowforge.local.yml`) but should prefer `flowfuse.yml` if present.

### Which customers would this be available to

Everyone - CE/Starter/Team/Enterprise

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate