clutter: Prepare input focus for IM event delivery

The clutter_input_focus_filter_key_event() function has been made
a more generic filter_event(). Besides its old role about letting
key events go through the IM, it will also process the IM events
that are possibly injected as a result.

Users have been updated to these changes.

https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1286

src/wayland/meta-wayland-text-input.c

@@ -737,6 +737,5 @@ meta_wayland_text_input_handle_event (MetaWaylandTextInput *text_input,
       !clutter_input_focus_is_focused (text_input->input_focus))
     return FALSE;
 
-  return clutter_input_focus_filter_key_event (text_input->input_focus,
-                                               (const ClutterKeyEvent *) event);
+  return clutter_input_focus_filter_event (text_input->input_focus, event);
 }