tests: qtest: Add virtio-iommu test

Add the framework to test the virtio-iommu-pci device
and tests exercising the attach/detach, map/unmap API.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Reviewed-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
Acked-by: Thomas Huth <thuth@redhat.com>
Message-Id: <20211127072910.1261824-5-eric.auger@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>