This does two things to frown upon:
- Modifies ClutterEvent structs, while the effort is to have those
  completely opaque, and readonly after creation from the input
  thread side.
- Stores state in the ClutterInputDevice struct, event though those
  are also considered static after creation, managed by the input
  thread, etc.

Stop doing that. This makes all events just forwarded as-is in
the ClutterStage/clutter-main.c code.

Handling of click count sounds like material for a ClutterGestureAction
(or perhaps ClutterClickAction), all of both callers now do it in place
at the moment, while gestures lack a better state tracking and management.

Part-of: <GNOME/mutter!2024>