[Virtio-GPU Venus] Allow sandboxing workarounds

Goal

According to libvirt/libvirt#638 (comment 2428871101) Virtio-GPU Venus seems to not work with sandboxing enabled, and currently there is no way to tell QEMU to not fork-exec virgl and instead have host application pass a virgl server fd to it, so that it will work with sandboxing.

Technical details

One of the comment in the above issue seems to have made a patch that allows passing the virgl chardev in the config and instruct QEMU to use that fd for virgl server.

Additional information

This is the patch mentioned in the technical details: patch