The generic vhost-user device took its virtio device type on the
command line via the `virtio_id` parameter, but the same value is
called `device_type` in the API and the resulting config struct. This
irregularity was due to churn during the review process, `device_type`
was the intended name.
Accept `device_type` on the command line and keep `virtio_id` as a
deprecated alias that logs a warning. The alias will then be removed in
a later release.
Fixes: #8545
Assisted-by: Claude:Opus-4.8
Signed-off-by: Rob Bradford <rbradford@meta.com>
