Emit less update events for odd FS events (#39557)

When running flycheck, I've noticed that scrolling starts to lag:


https://github.com/user-attachments/assets/b0bef0a3-ccbd-479d-a385-273398086d38

When checking the trace, it is notable that project panel updates its
entire tree multiple times during flycheck:

<img width="2032" height="1136" alt="image"
src="https://github.com/user-attachments/assets/d1935e77-3b00-4be5-a12a-8a17a9d64202"
/>


[scrolling.trace.zip](https://github.com/user-attachments/files/22710852/scrolling.trace.zip)

Turns out, `target/debug` directory is loaded by Zed (presumably,
reported by langserver as there are sources generated by bindgen and
proto that need to be loaded), and `target/debug/build` directory
received multiple events of a `None` kind for Zed, which trigger the
rescans.

Rework the logic to omit the `None`-kind events in Zed, and to avoid
excessive repo updates if not needed.


Release Notes:

- Improved worktree FS event emits in gitignored directories

---------

Co-authored-by: Cole Miller <cole@zed.dev>

crates/worktree/src/worktree.rs

@@ -3644,8 +3644,14 @@ impl BackgroundScanner {
             while let Poll::Ready(Some(more_paths)) = futures::poll!(fs_events_rx.next()) {
                 paths.extend(more_paths);
             }
-            self.process_events(paths.into_iter().map(Into::into).collect())
-                .await;
+            self.process_events(
+                paths
+                    .into_iter()
+                    .filter(|e| e.kind.is_some())
+                    .map(Into::into)
+                    .collect(),
+            )
+            .await;
         }
         if let Some(abs_path) = containing_git_repository {
             self.process_events(vec![abs_path]).await;
@@ -3690,7 +3696,7 @@ impl BackgroundScanner {
                     while let Poll::Ready(Some(more_paths)) = futures::poll!(fs_events_rx.next()) {
                         paths.extend(more_paths);
                     }
-                    self.process_events(paths.into_iter().map(Into::into).collect()).await;
+                    self.process_events(paths.into_iter().filter(|e| e.kind.is_some()).map(Into::into).collect()).await;
                 }
 
                 paths = global_gitignore_events.next().fuse() => {