WindowServer: Add const version of Menu::find_menu_by_id(int menu_id)

It's a little sad having two diferent versions of this function, but I
don't know of any better way to do it. This also gets rid of some const
casts down the line.

Services/WindowServer/ClientConnection.h

@@ -72,6 +72,13 @@ class ClientConnection final
  return nullptr;
  return const_cast<Menu*>(menu.value().ptr());
  }
+ const Menu* find_menu_by_id(int menu_id) const
+ {
+ auto menu = m_menus.get(menu_id);
+ if (!menu.has_value())
+ return nullptr;
+ return menu.value().ptr();
+ }
 
  void notify_display_link(Badge<Compositor>);