qapi: add native list coverage for QMP input visitor tests

This exercises schema-generated visitors for native list types and does
some sanity checking on validity of deserialized data.

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Amos Kong <akong@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
