clutter: Make all event subtype typedefs an alias of ClutterEvent

On the outside it does not matter anymore, since the various ClutterEvent methods do check events being of the right type. But we use these subtype typedefs in ClutterActor vmethods, and those are picked up by g-i, and used (for direct struct access, since these are not quite ClutterEvents to g-i/GJS, thus getter methods aren't allowed).

In order to ease things to move in the right direction in the GNOME Shell side, and being able to use ClutterEvent getter methods in ClutterActor vfuncs, make all these type names aliases of ClutterEvent, so that we do not need to change ClutterActor subclasses in one go, while letting g-i/GJS pick up the right type/alias and allow using the getter methods.