Make it possible to have stateful connections

A typical usecase involves authenticating to a remote server.

I first thought this would be easy enough: See this example https://github.com/n0-computer/irpc/blob/main/irpc-iroh/examples/auth.rs

There's a Auth message that contains whatever authentication token you are using. The server expects the first message on a connection to be that message, and aborts the connection if not or if the token doesn't verify. From the server side, all is good.

On the client side however, it seems to be fine to just issue an Auth rpc call when constructing a client. However, it is not: the RemoteConnection impls for both irpc over quic and irpc-iroh support reconnects-on-demand: If the previous connection was aborted by the server in-between (e.g. because the server was restarted), irpc will reconnect to the server with the same args (alpn and node addr) than in the initial connection. The request submitted by the application will then be sent on the new connection - which will fail, because the server expects an Auth message as the first message on each connection.

It is currently completely invisible to the irpc::Client and application code if and when such reconnections happend, therefore there's no way currently to "send an Auth request first whenever a reconnect happens".

Fixing this is quite important to me, I have multiple uses of irpc that would need this. The only alternative currently is to send a token with each and every request, which is wasteful and cumbersome.

Start with the auth.rs example and the RemoteConnection implementations for irpc over QUIC and irpc-iroh, then trace how irpc::Client handles reconnects. Define a connection-lifecycle mechanism for stateful setup, and verify that authentication is sent before application requests after every reconnect.