Use a single Flagsmith project for Flagsmith-on-Flagsmith

Currently, we expect two distinct FoF projects for Core API and Frontend.

To simplify our delivery infra and increase visibility, we should work on moving a single Flagsmith project for the entirety of the codebase. Ideally, I see us agreeing on a convention where we use the same project for other moving parts of Flagsmith (Edge API, Edge Proxy, SDKs) as well.