ssh remoting: Add infrastructure to handle reconnects (#18572)

This restructures the code in `remote` so that it's easier to replace
the current SSH connection with a new one in case of
disconnects/reconnects.

Right now, it successfully reconnects, BUT we're still missing the big
piece on the server-side: keeping the server process alive and
reconnecting to the same process that keeps the project-state.

Release Notes:

- N/A

---------

Co-authored-by: Bennet <bennet@zed.dev>

crates/project/src/terminals.rs

@@ -67,8 +67,12 @@ impl Project {
     }
 
     fn ssh_command(&self, cx: &AppContext) -> Option<SshCommand> {
-        if let Some(ssh_session) = self.ssh_session.as_ref() {
-            return Some(SshCommand::Direct(ssh_session.ssh_args()));
+        if let Some(args) = self
+            .ssh_client
+            .as_ref()
+            .and_then(|session| session.ssh_args())
+        {
+            return Some(SshCommand::Direct(args));
         }
 
         let dev_server_project_id = self.dev_server_project_id()?;