Add virtio-net Control Virtqueue state restore support

Virtio-net device uses Control Virtqueue(CVQ) for changing device parameters. For some devices, such as vDPA, its CVQ is passed from Guest’s driver directly to Host driver, which makes it difficult for QEMU to track the status of these devices. To solve this problem, QEMU introduces Shadow Virtqueue(SVQ) for vdpa device, which shadows the CVQ via QEMU instead of being assigned directly to Guest. During QEMU Live migration, to restore the vdpa device in the destination VM to the state in the source VM, SVQ can use CVQ’s interface and send the state as regular CVQ commands. Due to some CVQ commands for vDPA are missing at present, this project aims to achieve support for a subset of CVQ commands, including VIRTIO_NET_CTRL_RX family commands, VIRTIO_NET_CTRL_GUEST_OFFLOADS_SET command, VIRTIO_NET_CTRL_VLAN_ADD command, VIRTIO_NET_CTRL_MQ_HASH_CONFIG command and VIRTIO_NET_CTRL_MQ_RSS_CONFIG command for vDPA.