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 from crosvm with some
minor modification to rutabaga crate to fix compilation.
This crate depends on this PR[rust-vmm/vhost#239]
that implements support for QEMU's vhost-user-gpu protocol.

This device uses the rutabaga_gfx crate to offer two rendering backends:
1. Virglrenderer:
   - Rutabaga translates OpenGL API and Vulkan calls to an intermediate
     representation and allows for OpenGL acceleration on the host.
2. Gfxstream:
   - GLES and Vulkan calls are forwarded to the host.

These backends can be used by simply changing the `--gpu-mode` 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

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>

Author: Dorinda Bassey