Initial compositor submit, Vulkan only for now
Transition texture to VK_IMAGE_LAYOUT_TRANSFER_SRC_OPTIMAL
Poll events & get poses correctly
Check error inside PollEvents
Clear first draw
Don't do blit copy for each eye (works as long as `r_aoproxy_enable 00`)
https://files.facepunch.com/alexguthrie/1b1311b1/qrenderdoc_wLfY06ol2a.png
Submit & impl submit for DX11