Implement XR_MND_egl_enable
This extension introduces a more robust way of creating an XrSession for OpenGL. It also lays the groundwork for future OpenGL ES support.
https://github.com/KhronosGroup/OpenXR-Docs/pull/40
An implementation of this for hello_xr is available here for testing: https://github.com/emersion/OpenXR-SDK-Source/tree/hello-egl