Allow OpenGL calls in render loop

[natevm]

I had someone reach out and ask if it might be possible to use immediate mode opengl calls inside the renderloop to rasterize lines and other debugging symbols on top of the ray traced final image.

This could be made possible by using OpenGL and Vulkan interop in the GPRT backend.

Open questions

• How might this impact profiling?
• What about performance over a native Vulkan solution?