Add FocusLock to emoji picker (#31146)

* Add focus lock to emoji picker and e2e test.

* Remove direct use of FocusLock in favour of the ContextMenu prop.

* Apply returnFocus for ContextMenu focusLocks

* Remove import

src/components/structures/ContextMenu.tsx

@@ -405,7 +405,7 @@ export default class ContextMenu extends React.PureComponent<React.PropsWithChil
         );
 
         if (focusLock) {
-            body = <FocusLock>{body}</FocusLock>;
+            body = <FocusLock returnFocus>{body}</FocusLock>;
         }
 
         // filter props that are invalid for DOM elements