Based on Beyley's initial draft in #11601.
Co-authored-by: Beyley Cardellio <ep1cm1n10n123@gmail.com>
Co-authored-by: Ethan Lee <flibitijibibo@gmail.com>
SDL_CreateGPURenderer() now allows passing in an existing GPU device and passing in a NULL window to create an offscreen renderer.
Also renamed SDL_SetRenderGPUState() to SDL_SetGPURenderState().