xmlstream: implement simple timeout logic

This allows to detect and handle dying streams without getting stuck
forever.

Timeouts are always wrong, though, so we put the burden of choosing the
right values (mostly) on the creator of a stream.

tokio-xmpp/src/connect/starttls.rs

@@ -44,7 +44,7 @@ use crate::{
     connect::{DnsConfig, ServerConnector, ServerConnectorError},
     error::{Error, ProtocolError},
     xmlstream::{
-        initiate_stream, PendingFeaturesRecv, ReadError, StreamHeader, XmppStream,
+        initiate_stream, PendingFeaturesRecv, ReadError, StreamHeader, Timeouts, XmppStream,
         XmppStreamElement,
     },
     Client,
@@ -70,6 +70,7 @@ impl ServerConnector for StartTlsServerConnector {
         &self,
         jid: &Jid,
         ns: &'static str,
+        timeouts: Timeouts,
     ) -> Result<PendingFeaturesRecv<Self::Stream>, Error> {
         let tcp_stream = tokio::io::BufStream::new(self.0.resolve().await?);
 
@@ -82,6 +83,7 @@ impl ServerConnector for StartTlsServerConnector {
                 from: None,
                 id: None,
             },
+            timeouts,
         )
         .await?;
         let (features, xmpp_stream) = xmpp_stream.recv_features().await?;
@@ -98,6 +100,7 @@ impl ServerConnector for StartTlsServerConnector {
                     from: None,
                     id: None,
                 },
+                timeouts,
             )
             .await?)
         } else {