Since virtio-gpu context types are now in upstream kernels, it is now
possible to use Sommelier without patching it or using custom kernels,
so I think it's finally suitable for inclusion in Nixpkgs.
I'm using the same versioning scheme I made up for crosvm here.
Figuring out the version is handled by the update script, which I
adapted from the crosvm one. Sadly there's too many differences
between them to easily merge them into one, so reducing duplication
between them is left as further work.
Closes: https://github.com/NixOS/nixpkgs/pull/95874
