Selecting a server that doesn't support login now fails instead of letting you continue to a failure later. (#3342)

* Fail configuration of the authentication service if the homeserver doesn't support login.

* Move the ServerSelectionCoordinator logic into the ViewModel.

- Handle the new login alert.
- Add more tests

ElementX/Sources/Services/Authentication/AuthenticationService.swift

@@ -65,6 +65,9 @@ class AuthenticationService: AuthenticationServiceProtocol {
             case .failure: nil
             }
             
+            if flow == .login, homeserver.loginMode == .unsupported {
+                return .failure(.loginNotSupported)
+            }
             if flow == .register, !homeserver.supportsRegistration {
                 return .failure(.registrationNotSupported)
             }