editor: Shrink DisplayMapSnapshot from 824 to 256 bytes (#39568)

We have unnecessary clones for the fields here as most of the snapshots
contain the others hierarchically.

Release Notes:

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

crates/diagnostics/src/diagnostic_renderer.rs

@@ -138,7 +138,7 @@ impl editor::DiagnosticRenderer for DiagnosticRenderer {
                 BlockProperties {
                     placement: BlockPlacement::Near(
                         snapshot
-                            .buffer_snapshot
+                            .buffer_snapshot()
                             .anchor_after(block.initial_range.start),
                     ),
                     height: Some(1),
@@ -278,7 +278,7 @@ impl DiagnosticBlock {
             }
         } else if let Some(diagnostic) = editor
             .snapshot(window, cx)
-            .buffer_snapshot
+            .buffer_snapshot()
             .diagnostic_group(buffer_id, group_id)
             .nth(ix)
         {

crates/diagnostics/src/diagnostics_tests.rs

@@ -863,20 +863,20 @@ async fn test_random_diagnostics_with_inlays(cx: &mut TestAppContext, mut rng: S
             21..=50 => mutated_diagnostics.update_in(cx, |diagnostics, window, cx| {
                 diagnostics.editor.update(cx, |editor, cx| {
                     let snapshot = editor.snapshot(window, cx);
-                    if !snapshot.buffer_snapshot.is_empty() {
-                        let position = rng.random_range(0..snapshot.buffer_snapshot.len());
-                        let position = snapshot.buffer_snapshot.clip_offset(position, Bias::Left);
+                    if !snapshot.buffer_snapshot().is_empty() {
+                        let position = rng.random_range(0..snapshot.buffer_snapshot().len());
+                        let position = snapshot.buffer_snapshot().clip_offset(position, Bias::Left);
                         log::info!(
                             "adding inlay at {position}/{}: {:?}",
-                            snapshot.buffer_snapshot.len(),
-                            snapshot.buffer_snapshot.text(),
+                            snapshot.buffer_snapshot().len(),
+                            snapshot.buffer_snapshot().text(),
                         );
 
                         editor.splice_inlays(
                             &[],
                             vec![Inlay::edit_prediction(
                                 post_inc(&mut next_inlay_id),
-                                snapshot.buffer_snapshot.anchor_before(position),
+                                snapshot.buffer_snapshot().anchor_before(position),
                                 Rope::from_iter(["Test inlay ", "next_inlay_id"]),
                             )],
                             cx,