Provides several important improvements to the runtime action
bindings operation and internal API.

Moves input-specific action data (input thresholds, input regions,
pose offsets/spaces) from actions to more granular action bindings.
This allows a single action to be mapped to a variety of inputs,
without having to share a single input threshold, region, or space.

This also removes the need for action space creation API, as spaces
for pose actions will be automatically created with the bindings.

The correct action data for the current inputs is set by calling
xrGetCurrentInteractionProfile() to get the current profile and then
retrieving the corresponding mapped data.

Does not bring about any changes for users since only internal
runtime functionality is currently affected.

Is not dependent on the other VR patches, although it may be useful
to address this before D10943 (actionmaps) since it will affect the
upcoming RNA API.