sidebar: Improve performance of rebuild_contents (#57717)

Release Notes:

- N/A or Added/Fixed/Improved ...

crates/action_log/src/action_log.rs

@@ -936,7 +936,11 @@ impl ActionLog {
         let mut undo_buffers = Vec::new();
         let mut futures = Vec::new();
 
-        for buffer in self.changed_buffers(cx).into_keys() {
+        for buffer in self
+            .changed_buffers(cx)
+            .map(|(buffer, _)| buffer)
+            .collect::<Vec<_>>()
+        {
             let buffer_ranges = vec![Anchor::min_max_range_for_buffer(
                 buffer.read(cx).remote_id(),
             )];
@@ -1023,17 +1027,19 @@ impl ActionLog {
     }
 
     /// Returns the set of buffers that contain edits that haven't been reviewed by the user.
-    pub fn changed_buffers(&self, cx: &App) -> BTreeMap<Entity<Buffer>, Entity<BufferDiff>> {
+    pub fn changed_buffers(
+        &self,
+        cx: &App,
+    ) -> impl Iterator<Item = (Entity<Buffer>, Entity<BufferDiff>)> {
         self.tracked_buffers
             .iter()
             .filter(|(_, tracked)| tracked.has_edits(cx))
             .map(|(buffer, tracked)| (buffer.clone(), tracked.diff.clone()))
-            .collect()
     }
 
     /// Returns the total number of lines added and removed across all unreviewed buffers.
     pub fn diff_stats(&self, cx: &App) -> DiffStats {
-        DiffStats::all_files(&self.changed_buffers(cx), cx)
+        DiffStats::all_files(self.changed_buffers(cx), cx)
     }
 
     /// Iterate over buffers changed since last read or edited by the model
@@ -1079,7 +1085,7 @@ impl DiffStats {
     }
 
     pub fn all_files(
-        changed_buffers: &BTreeMap<Entity<Buffer>, Entity<BufferDiff>>,
+        changed_buffers: impl IntoIterator<Item = (Entity<Buffer>, Entity<BufferDiff>)>,
         cx: &App,
     ) -> Self {
         let mut total = DiffStats::default();
@@ -3254,21 +3260,21 @@ mod tests {
             child_log_1
                 .read(cx)
                 .changed_buffers(cx)
-                .into_keys()
+                .map(|(buffer, _)| buffer)
                 .collect()
         });
         let child_2_changed: Vec<_> = cx.read(|cx| {
             child_log_2
                 .read(cx)
                 .changed_buffers(cx)
-                .into_keys()
+                .map(|(buffer, _)| buffer)
                 .collect()
         });
         let parent_changed: Vec<_> = cx.read(|cx| {
             parent_log
                 .read(cx)
                 .changed_buffers(cx)
-                .into_keys()
+                .map(|(buffer, _)| buffer)
                 .collect()
         });
 
@@ -3494,7 +3500,6 @@ mod tests {
             action_log
                 .read(cx)
                 .changed_buffers(cx)
-                .into_iter()
                 .map(|(buffer, diff)| {
                     let snapshot = buffer.read(cx).snapshot();
                     (