In preparation for creating another non-KMS backend virtual CRTC. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>
There is going to me another non-abstract MetaCrtcNative type, just as there will be for MetaOutputNative. Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>