vfio: Introduce base object for VFIOContainer and targeted interface

vfio: Introduce base object for VFIOContainer and targeted interface

Introduce a dumb VFIOContainerBase object and its targeted interface.
This is willingly not a QOM object because we don't want it to be
visible from the user interface. The VFIOContainerBase will be
smoothly populated in subsequent patches as well as interfaces.

No functional change intended.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
Signed-off-by: Yi Sun <yi.y.sun@linux.intel.com>
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@intel.com>
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Cédric Le Goater <clg@redhat.com>