Driver support for virtio objects

[Gnurou]

While the specification mentions how virtio objects can be imported and exported, the guest driver does not support this yet. The main obstacle is figuring out how to test this with an upstream kernel, and probably virtio-gpu.

[aesteve-rh]

Let me bring to your attention, in case it helps, that rust-vmm has a relatively new, WiP implementation of virtio-gpu that may be useful for testing this feature: https://github.com/rust-vmm/vhost-device/tree/main/staging/vhost-device-gpu

Testing is indeed going to be a challenge, but when the time comes, we can work together to figure it out.

cc: @dorindabassey @mtjhrc