editor: Remove buffer and display map fields from SelectionsCollection (#42175)

Release Notes:

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

crates/diagnostics/src/diagnostics.rs

@@ -315,11 +315,15 @@ impl ProjectDiagnosticsEditor {
         cx: &mut Context<Self>,
         retain_selections: bool,
     ) {
-        let buffer_ids = self.multibuffer.read(cx).all_buffer_ids();
-        let selected_buffers = self.editor.update(cx, |editor, cx| {
+        let snapshot = self
+            .editor
+            .update(cx, |editor, cx| editor.display_snapshot(cx));
+        let buffer = self.multibuffer.read(cx);
+        let buffer_ids = buffer.all_buffer_ids();
+        let selected_buffers = self.editor.update(cx, |editor, _| {
             editor
                 .selections
-                .all_anchors(cx)
+                .all_anchors(&snapshot)
                 .iter()
                 .filter_map(|anchor| anchor.start.buffer_id)
                 .collect::<HashSet<_>>()

crates/diagnostics/src/diagnostics_tests.rs

@@ -156,7 +156,9 @@ async fn test_diagnostics(cx: &mut TestAppContext) {
     // Cursor is at the first diagnostic
     editor.update(cx, |editor, cx| {
         assert_eq!(
-            editor.selections.display_ranges(cx),
+            editor
+                .selections
+                .display_ranges(&editor.display_snapshot(cx)),
             [DisplayPoint::new(DisplayRow(3), 8)..DisplayPoint::new(DisplayRow(3), 8)]
         );
     });
@@ -232,7 +234,9 @@ async fn test_diagnostics(cx: &mut TestAppContext) {
     // Cursor keeps its position.
     editor.update(cx, |editor, cx| {
         assert_eq!(
-            editor.selections.display_ranges(cx),
+            editor
+                .selections
+                .display_ranges(&editor.display_snapshot(cx)),
             [DisplayPoint::new(DisplayRow(8), 8)..DisplayPoint::new(DisplayRow(8), 8)]
         );
     });