net/virtio: add election for vectorized path

net/virtio: add election for vectorized path

Rewrite vectorized path selection logic. Default setting comes from
vectorized devarg, then checks each criteria.

Packed ring vectorized path need:
    AVX512F and required extensions are supported by compiler and host
    VERSION_1 and IN_ORDER features are negotiated
    mergeable feature is not negotiated
    LRO offloading is disabled

Split ring vectorized rx path need:
    mergeable and IN_ORDER features are not negotiated
    LRO, chksum and vlan strip offloadings are disabled

Signed-off-by: Marvin Liu <yong.liu@intel.com>
Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>