Port the EdgeDragAction to ClutterGesture

Port the EdgeDragAction to ClutterGesture

And since ClutterGestures will only be possible to implement in C (due to
performance concerns when we'll get rid of motion event compression and
start handling eg. 1000 HZ mouse events at the full rate), that means we
have to port the gesture to C!

It behaves mostly the same still: It's a single finger touch-only gesture
that recognizes as soon as a point that began on the monitor edge moves away
from that edge. It then emits "progress" signals with the distance from the
edge all the way until the fixed threshold distance (DRAG_DISTANCE) is
reached, where it then moves to COMPLETED.

There's definitely room for further improvements here, eg. the gesture
should probably only complete once the point is lifted from the screen.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2853>