Allow disk-based diagnostic progress begin/end events to interleave

When multiple saves occur, we can have multiple start events followed by multiple end events. We don't want to update our project diagnostics view until all pending progress is finished.

Co-Authored-By: Antonio Scandurra <me@as-cii.com>

crates/editor/src/test.rs

@@ -1,33 +1,6 @@
-use gpui::{Entity, ModelHandle};
-use smol::channel;
-use std::marker::PhantomData;
-
 #[cfg(test)]
 #[ctor::ctor]
 fn init_logger() {
     // std::env::set_var("RUST_LOG", "info");
     env_logger::init();
 }
-
-pub struct Observer<T>(PhantomData<T>);
-
-impl<T: 'static> Entity for Observer<T> {
-    type Event = ();
-}
-
-impl<T: Entity> Observer<T> {
-    pub fn new(
-        handle: &ModelHandle<T>,
-        cx: &mut gpui::TestAppContext,
-    ) -> (ModelHandle<Self>, channel::Receiver<()>) {
-        let (notify_tx, notify_rx) = channel::unbounded();
-        let observer = cx.add_model(|cx| {
-            cx.observe(handle, move |_, _, _| {
-                let _ = notify_tx.try_send(());
-            })
-            .detach();
-            Observer(PhantomData)
-        });
-        (observer, notify_rx)
-    }
-}