* Replace Rust's Authentication service by building a Client.
* Drop the Proxy from AuthenticationServiceProxy[Protocol].
* Make sure to call abortOIDCLogin.
* Centralise common ClientBuilder code.
* Update the SDK.
* Present OIDC directly on the ServerConfirmationScreen.
Read the actual window from the view.
* Pop back to the confirmation screen when a user enters an MXID that needs OIDC.
* Remove OIDC error handling from the login screen.
