st/oxr: Implement xrEnumerateBoundSourcesForAction
I think this is what the function is supposed to do.
Output from my test code:
Grab action has 4 sources
Grab Source 0: /user/hand/left/input/select/click
Grab Source 1: /user/hand/left/input/select
Grab Source 2: /user/hand/right/input/select/click
Grab Source 3: /user/hand/right/input/select