Windows support

[stgraber]

The virtio drivers for Windows now include a signed vsock driver as well as logic to add the socket type to a Windows system.

It would be great if we could get support for Windows in this package to then easily get things like the Incus agent working over vsock.

Example logic (C) from the VirtIO drivers: https://github.com/virtio-win/kvm-guest-drivers-windows/blob/master/viosock/viosocklib-test/viosocklib-test.c