Add session on ProxyHttp#new_ctx function

[taikulawo]

1. Add session when call new_ctx
   we need some args when create new_ctx
2. make HttpProxy#new public
   We don't create service, just call Service::handle_event with our custom Box<dyn IO>
   How to get additional input when call new_ctx? #316
3. make from_wire_selected public
   we use custom Box<dyn IO>, so we need create ALPN

impl<T> Ssl for PingoraStream<T> {
    fn get_ssl_digest(&self) -> Option<Arc<pingora::protocols::ssl::SslDigest>> {
        None
    }
    fn selected_alpn_proto(&self) -> Option<ALPN> {
        self.tls_info
            .as_ref()
            .and_then(|c| c.selected_alpn.as_ref())
            .and_then(|f| ALPN::from_wire_selected(f))
    }
}