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/remote/src/remote.rs

@@ -2,4 +2,4 @@ pub mod json_log;
 pub mod protocol;
 pub mod ssh_session;
 
-pub use ssh_session::{SshClientDelegate, SshConnectionOptions, SshPlatform, SshSession};
+pub use ssh_session::{SshClientDelegate, SshConnectionOptions, SshPlatform, SshRemoteClient};