vfio/common: Move legacy VFIO backend code into separate container.c

vfio/common: Move legacy VFIO backend code into separate container.c

Move all the code really dependent on the legacy VFIO container/group
into a separate file: container.c. What does remain in common.c is
the code related to VFIOAddressSpace, MemoryListeners, migration and
all other general operations.

Signed-off-by: Eric Auger <eric.auger@redhat.com>
Signed-off-by: Yi Liu <yi.l.liu@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>