Cyborg Intel PMEM driver support PMEM Namespace management

Persistent memory (or pmem for short) is accessed like volatile memory, using processor load and store instructions, but it retains its contents across power loss like storage. In nova the Persistent memory namespace management and resource tracking as following[1]:
1. Custom Resource Classes are used to represent persistent memory namespace resource. The naming convention of the custom resource classes being used is "CUSTOM_PMEM_NAMESPACE_$LABEL".
2. The association between $LABEL and persistent memory namespaces is defined by a new configuration option ‘CONF.libvirt.pmem_namespaces’. This config option is of string type in below format "$LABEL:$NSNAME[|$NSNAME][,$LABEL:$NSNAME[|$NSNAME]]".

[1] https://specs.openstack.org/openstack/nova-specs/specs/train/implemented/virtual-persistent-memory.html#persistent-memory-namespace-management-and-resource-tracking