The test makes sure the YCbCr formats create the expected image and we
don't accidentally break it.
Like all wayland tests, this is now part of mutter/wayland, mutter/tty,
and mutter/kvm and will use either shm or dma-buf depending on which
suite is chosen.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3371>