Add option to read and decode On Demand state certificates.

Link: https://github.com/intel/intel-sdsi/blob/master/state-certificate-encoding.rstSigned-off-by: David E. Box <david.e.box@linux.intel.com>
Reviewed-by: Hans de Goede <hdegoede@redhat.com>
Link: https://lore.kernel.org/r/20221119002343.1281885-6-david.e.box@linux.intel.comSigned-off-by: Hans de Goede <hdegoede@redhat.com>