repl: Add restart kernel action and improve shutdown (#16609)

- Implement restart kernel functionality
- Clean up shutdown process to properly drop messaging and exit status
tasks
- Refactor kernel state handling for better consistency

Closes #16037

Release Notes:

- repl: Added restart kernel action
- repl: Fixed issue with shutting down kernels that are in a failure
state

crates/repl/src/repl_sessions_ui.rs

@@ -23,6 +23,7 @@ actions!(
         Sessions,
         Interrupt,
         Shutdown,
+        Restart,
         RefreshKernelspecs
     ]
 );
@@ -126,6 +127,19 @@ pub fn init(cx: &mut AppContext) {
                 }
             })
             .detach();
+
+        editor
+            .register_action({
+                let editor_handle = editor_handle.clone();
+                move |_: &Restart, cx| {
+                    if !JupyterSettings::enabled(cx) {
+                        return;
+                    }
+
+                    crate::restart(editor_handle.clone(), cx);
+                }
+            })
+            .detach();
     })
     .detach();
 }