This commit adds to debug menu toggle to show Unreal Engine FPS counter
and engine statistics.

This provides non obnoxious way to have them on screen at all times.
Stats appear in top left corner just outside of your normal field of
vision. This allows you to turn them on and keep them on compared to
Virtual Desktop overlay.

Compared to OpenXR toolkit this way is much more compatible with UEVR.
Current builds of OpenXR increase number of crashes.