Of it, the backends read the EFB scale, now passed as the backbuffer
scale; GLContext::Create tested for libretro, its only context; and
the controller interface kept a render window that is always null. The
video backends' Initialize, InitBackendInfo and PopulateBackendInfo,
Core::Init, EmuThread and StartEmuThread, BootCore and the controller
interface lose the parameter; PrepareWindow, ChangeWindow, the window
change refresh and the Vulkan instance's surface extensions go, as
nothing presents but the frontend.
This specific issue was already addressed by https://github.com/dolphin-emu/dolphin/pull/11635
though I felt like there was something more we could do, and wasn't too happy with the
likelihood of devices update calls being skipped (due to `m_devices_population_mutex` being locked).