Fix cleanup of LSP request status messages (#10336)

This fixes a bug in https://github.com/zed-industries/zed/pull/9818,
where the status was not removed if the request failed. It also adds
replication of these new status messages to guests when collaborating.

Release Notes:

- Fixed an issue where the status of failed LSP actions was left in the
status bar

---------

Co-authored-by: Marshall <marshall@zed.dev>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/gpui/src/app/test_context.rs

@@ -463,7 +463,7 @@ impl TestAppContext {
     }
 }
 
-impl<T: Send> Model<T> {
+impl<T: 'static> Model<T> {
     /// Block until the next event is emitted by the model, then return it.
     pub fn next_event<Evt>(&self, cx: &mut TestAppContext) -> Evt
     where
@@ -491,6 +491,31 @@ impl<T: Send> Model<T> {
         }
         panic!("no event received")
     }
+
+    /// Returns a future that resolves when the model notifies.
+    pub fn next_notification(&self, cx: &TestAppContext) -> impl Future<Output = ()> {
+        use postage::prelude::{Sink as _, Stream as _};
+
+        let (mut tx, mut rx) = postage::mpsc::channel(1);
+        let mut cx = cx.app.app.borrow_mut();
+        let subscription = cx.observe(self, move |_, _| {
+            tx.try_send(()).ok();
+        });
+
+        let duration = if std::env::var("CI").is_ok() {
+            Duration::from_secs(5)
+        } else {
+            Duration::from_secs(1)
+        };
+
+        async move {
+            let notification = crate::util::timeout(duration, rx.recv())
+                .await
+                .expect("next notification timed out");
+            drop(subscription);
+            notification.expect("model dropped while test was waiting for its next notification")
+        }
+    }
 }
 
 impl<V: 'static> View<V> {