Restructure remote client crate, consolidate SSH logic (#36967)

This is a pure refactor that consolidates all SSH remoting logic such
that it should be straightforward to add another transport to the
remoting system.

Release Notes:

- N/A

---------

Co-authored-by: Mikayla Maki <mikayla.c.maki@gmail.com>

crates/debugger_ui/src/session/running.rs

@@ -916,10 +916,11 @@ impl RunningState {
         let task_store = project.read(cx).task_store().downgrade();
         let weak_project = project.downgrade();
         let weak_workspace = workspace.downgrade();
-        let ssh_info = project
+        let remote_shell = project
             .read(cx)
-            .ssh_client()
-            .and_then(|it| it.read(cx).ssh_info());
+            .remote_client()
+            .as_ref()
+            .and_then(|remote| remote.read(cx).shell());
 
         cx.spawn_in(window, async move |this, cx| {
             let DebugScenario {
@@ -1003,7 +1004,7 @@ impl RunningState {
                     None
                 };
 
-                let builder = ShellBuilder::new(ssh_info.as_ref().map(|info| &*info.shell), &task.resolved.shell);
+                let builder = ShellBuilder::new(remote_shell.as_deref(), &task.resolved.shell);
                 let command_label = builder.command_label(&task.resolved.command_label);
                 let (command, args) =
                     builder.build(task.resolved.command.clone(), &task.resolved.args);