SSH remoting: terminal & tasks (#15321)

This also rolls back the `TerminalWorkDir` abstraction I added for the
original remoting, and tidies up the terminal creation code to be clear
about whether we're creating a task *or* a terminal. The previous logic
was a little muddy because it assumed we could be doing both at the same
time (which was not true).

Release Notes:

- remoting alpha: Removed the ability to specify `gh cs ssh` or `gcloud
compute ssh` etc. See https://zed.dev/docs/remote-development for
alternatives.
- remoting alpha: Added support for terminal and tasks to new
experimental ssh remoting

crates/project/src/prettier_support.rs

@@ -515,7 +515,8 @@ impl Project {
         buffer: &Model<Buffer>,
         cx: &mut ModelContext<Self>,
     ) -> Task<Option<(Option<PathBuf>, PrettierTask)>> {
-        if !self.is_local() {
+        // todo(ssh remote): prettier support
+        if self.is_remote() || self.ssh_session.is_some() {
             return Task::ready(None);
         }
         let buffer = buffer.read(cx);