tests/qtest: Add intel-iommu test

tests/qtest: Add intel-iommu test

Add the framework to test the intel-iommu device.

Currently only tested cap/ecap bits correctness when x-flts=on in scalable
mode. Also tested cap/ecap bits consistency before and after system reset.

Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Acked-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Clément Mathieu--Drif<clement.mathieu--drif@eviden.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Message-Id: <20241212083757.605022-21-zhenzhong.duan@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>