Addresses the remaining portions of T77137 (Python API for Controller Interaction), which was partially completed by D10942. Adds an XR "action maps" system for loading XR action data from a Python script. Action maps are accessible via the Python API, and are used to pass default actions to the VR session during the xr_session_start_pre() callback. Since action maps are stored only as runtime data, they will be cleaned up with the rest of the VR runtime data on file read or exit. Reviewed By: Julian Eisel, Hans Goudey Differential Revision: https://developer.blender.org/D10943