feat(remote-dev): forward ports of the remote host (#1131)

Remote windows get a Ports tool window: forward localhost:<port> of the remote host to this machine (same port when free here), with Open in Browser / Copy / Stop. Forwarded ports are remembered per host and folder and forwarded again on reconnect. Tunnels reuse the window's SSH session (ide_ssh::Tunnel can prefer a local port) and close with the connection.

Closes #819

crates/ide-ssh/src/tunnel.rs

@@ -26,7 +26,19 @@ impl Tunnel {
 
     /// [`Tunnel::open`] without the reachability check (the target may start later).
     pub async fn listen(session: Arc<Session>, host: &str, port: u16) -> IdeResult<Tunnel> {
-        let listener = TcpListener::bind(("127.0.0.1", 0)).await?;
+        Self::listen_on(session, None, host, port).await
+    }
+
+    /// [`Tunnel::listen`] on local port `preferred` when it is free, else on any free port
+    /// (a forwarded remote port keeps its number locally when it can, like VS Code's Ports).
+    pub async fn listen_on(session: Arc<Session>, preferred: Option<u16>, host: &str, port: u16) -> IdeResult<Tunnel> {
+        let listener = match preferred {
+            Some(p) => match TcpListener::bind(("127.0.0.1", p)).await {
+                Ok(l) => l,
+                Err(_) => TcpListener::bind(("127.0.0.1", 0)).await?,
+            },
+            None => TcpListener::bind(("127.0.0.1", 0)).await?,
+        };
         let local = listener.local_addr()?.port();
         let accept = tokio::spawn(forward(listener, session.clone(), host.to_owned(), port));
         Ok(Tunnel { port: local, session, accept })