This introduces a new version of virtio-blk device. The default
virtio-blk provides synchronous processing of the queues, while this
new version relies on io_uring from the host kernel to provide an
asynchronous processing of the queues.
This new asynchronous version provides a huge performance improvement
compared to the default synchronous version.
Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>