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/collab/src/tests/test_server.rs

@@ -25,7 +25,7 @@ use node_runtime::NodeRuntime;
 use notifications::NotificationStore;
 use parking_lot::Mutex;
 use project::{Project, WorktreeId};
-use remote::SshSession;
+use remote::SshRemoteClient;
 use rpc::{
     proto::{self, ChannelRole},
     RECEIVE_TIMEOUT,
@@ -835,7 +835,7 @@ impl TestClient {
     pub async fn build_ssh_project(
         &self,
         root_path: impl AsRef<Path>,
-        ssh: Arc<SshSession>,
+        ssh: Arc<SshRemoteClient>,
         cx: &mut TestAppContext,
     ) -> (Model<Project>, WorktreeId) {
         let project = cx.update(|cx| {