js: Mass move to Clutter.Event getter methods in Clutter.Actor vfuncs

These traditionally got the various ClutterEvent subtype structs as their
argument, so it was not allowed to use ClutterEvent generic getter methods
in these vfuncs. These methods used direct access to struct fields instead.

This got spoiled with the move to make ClutterEvent opaque types, since
these are no longer public structs so GNOME Shell most silently failed to
fetch the expected values from event fields. But since they are not
ClutterEvents either, the getters could not be used on them.

Mutter is changing so that these vmethods all contain an alias to the
one and only Clutter.Event type, thus lifting those barriers, and making
it possible to use the ClutterEvent methods in these vfuncs.

Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2950
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2872>

js/ui/runDialog.js

@@ -123,7 +123,7 @@ class RunDialog extends ModalDialog.ModalDialog {
     }
 
     vfunc_key_release_event(event) {
-        if (event.keyval === Clutter.KEY_Escape) {
+        if (event.get_key_symbol() === Clutter.KEY_Escape) {
             this.close();
             return Clutter.EVENT_STOP;
         }