flutter_supabase auth.signOut() should trigger 'onUnauthenticated'

[seenickcode]

Feature request

Is your feature request related to a problem? Please describe.

It would be ideal to keep all auth state logic in a single place, such as here, but unfortunately, when calling signOut, nothing in this AuthState implementation gets triggered, thus making the user's code brittle, because we have to code logic like this to update the route stack, vs having it all done in our AuthState implementation.