* Merge the AuthenticationServer with the QRCodeLoginService.
* Merge AuthenticationClientBuilderFactory and AuthenticationClientBuilder into AuthenticationClientFactory
The separation is no longer needed now that password/OIDC login and QR code login have a similar API shape.
* Don't query the homeserver until confirming it (or selecting a different one).
* Setup the infrastructure to test AuthenticationService.
Implement basic tests for configuration & password login.
* Use the real AuthenticationService with a mock Client in all of the tests.
* Add tests for the ServerConfirmationScreenViewModel.
* Remove redundant view state and test for it.
