Disable cursor for review mode in the IDE

Also disables occurrences highlights & the line highlight for the review
mode.

Closes #44307

app/assets/javascripts/ide/lib/editor.js

@@ -65,6 +65,10 @@ export default class Editor {
         (this.instance = this.monaco.editor.createDiffEditor(domElement, {
           ...defaultEditorOptions,
           readOnly: true,
+          quickSuggestions: false,
+          occurrencesHighlight: false,
+          renderLineHighlight: 'none',
+          hideCursorInOverviewRuler: true,
         })),
       );

app/assets/stylesheets/pages/repo.scss

@@ -290,6 +290,10 @@
     .margin-view-overlays .delete-sign {
       opacity: 0.4;
     }
+
+    .cursors-layer {
+      display: none;
+    }
   }
 }

spec/javascripts/ide/lib/editor_spec.js

@@ -74,6 +74,10 @@ describe('Multi-file editor library', () => {
           },
           readOnly: true,
           scrollBeyondLastLine: false,
+          quickSuggestions: false,
+          occurrencesHighlight: false,
+          renderLineHighlight: 'none',
+          hideCursorInOverviewRuler: true,
         },
       );
     });