Multi-GPU output support on Wayland #1
There's still a lot to do:
- refactor udev to list all available GPUs
- refactor DrmBackend to use the outputs of all GPUs
- make Atomic Mode Setting work properly on multiple GPUs (it doesn't on my secondary GPU)
- create a new OpenGLBackend that contains multiple other backends
- enable EglGbmBackend to copy buffers from other GPUs
- enable EglStreamBackend to copy buffers from other GPUs
- enable hotplugging of GPUs?
BUG: 425586 BUG: 417323