Improve code folding to exclude folding line breaks in whitespace-sensitive languages (#13108)

<img width="1219" alt="Screenshot 2024-06-16 at 15 43 31"
src="https://github.com/zed-industries/zed/assets/87859239/dd05de16-7f20-4c88-9e95-021555b8b78b">
<img width="1219" alt="Screenshot 2024-06-16 at 15 45 10"
src="https://github.com/zed-industries/zed/assets/87859239/b1b78cdd-f34d-4ea3-9728-4741727a9643">

Updated the foldable_range method to exclude folding line breaks during
code folding in whitespace-sensitive languages like Python and YAML.
This adjustment ensures that folding behaves as expected, similar to
other code editors.

Ref #11614

Release Notes:

- Improved code folds to ignore trailing newlines

crates/editor/src/display_map.rs

@@ -983,8 +983,23 @@ impl DisplaySnapshot {
                     break;
                 }
             }
-            let end = end.unwrap_or(max_point);
-            Some((start..end, self.fold_placeholder.clone()))
+
+            let mut row_before_line_breaks = end.unwrap_or(max_point);
+            while row_before_line_breaks.row > start.row
+                && self
+                    .buffer_snapshot
+                    .is_line_blank(MultiBufferRow(row_before_line_breaks.row))
+            {
+                row_before_line_breaks.row -= 1;
+            }
+
+            row_before_line_breaks = Point::new(
+                row_before_line_breaks.row,
+                self.buffer_snapshot
+                    .line_len(MultiBufferRow(row_before_line_breaks.row)),
+            );
+
+            Some((start..row_before_line_breaks, self.fold_placeholder.clone()))
         } else {
             None
         }