vhost-device-gpu: Add Initial Implementation

This program is a vhost-user backend daemon that provides
VIRTIO GPU device emulation as specified in the VIRTIO Spec v.1.2
https://docs.oasis-open.org/virtio/virtio/v1.2/csd01/virtio-v1.2-csd01.html
This crate utilizes the rutabaga crate Imported from crosvm
This crate depends on this PR[rust-vmm/vhost#239]
that implements support for QEMU's vhost-user-gpu protocol.

This crate supports both gfxstream and virglrenderer library
either of these libraries can be used by simply changing the
`renderer` command line option.
This crate also includes some modifications from libkrun virtio-gpu device
https://github.com/containers/libkrun/tree/main/src/devices/src/virtio/gpu

This device can be tested following the instructions explained in the
README.md file under staging/vhost-device-gpu/.

Fixes: #598

Co-authored-by: Dorinda Bassey <dbassey@redhat.com>
Co-authored-by: Matej Hrica <mhrica@redhat.com>

Signed-off-by: Dorinda Bassey <dbassey@redhat.com>
Signed-off-by: Matej Hrica <mhrica@redhat.com>

staging/Cargo.toml

@@ -1,5 +1,6 @@
 [workspace]
 resolver = "2"
 members = [
+  "vhost-device-gpu",
   "vhost-device-video",
 ]