With the Oculus runtime, the VR session would freeze when taking off the HMD and putting it back on. This was caused by the deletion of graphics resources too early in the OpenXR state machine, at least for Oculus. The resources will now only be freed once the session is actually destroyed. Also fixes an issue where it wasn't possible to stop the session via the UI when the HMD was taken off. Reviewed By: Julian Eisel Differential Revision: https://developer.blender.org/D7635