Show remaining AuthState values

[bagintz]

Currently you are not showing all the AuthState values and it would be helpful to be able to use the ones you are hiding:

....
export 'src/auth/auth_controller.dart' show AuthAction, AuthController;
export 'src/auth/auth_state.dart'
    show
        AuthState,
        AuthStateListener,
        CredentialLinked,
        CredentialReceived,
        SignedIn,
        SigningIn,
        AuthFailed,
        DifferentSignInMethodsFound;
export 'src/auth/flows/phone_auth_flow.dart';
....

For example, I am seeing a state of FetchingProvidersForEmail in my app and would like to check for that and show a progress meter, the same as SigningIn