Support EXT_hand_interaction for overlay interactions

[Beyley]

wlx-overlay-s should support hand interactions for interacting with the overlay, with gestures like pinch/poke to click/drag, face palm towards user and pinch for show/hide bind, etc.

I tend to not have my controllers in my hands while I'm eating, but I'll be watching content using the overlay, and it'd be nice to be able to interact with the overlay at least in some form even when that's the case.

[mitsuami-megane]

Apparently there is a problem that there are 3 hand interaction extensions and none of them is being used universally.

WiVRn/WiVRn#238

[Beyley]

Apparently there is a problem that there are 3 hand interaction extensions and none of them is being used universally.

WiVRn/WiVRn#238

The EXT extension seems to be supported on Quest, so the MSFT one can be pretty much ignored. Two is at least better than three, but still not ideal.