Convert hardware.VirtCPUTopology to nova object

All objects that have data that may eventually be serialized across the
wire in RPC comms, stored in a database, or potentially change their
schema, should be nova.objects. This patch changes the staticmethods on
the nova.virt.hardware.VirtCPUTopology class to a collection of private
(and one public) regular functions in nova.virt.hardware that consume and
produce nova.objects.virt_cpu_topology.VirtCPUTopology objects.

Change-Id: I2244aa7125b11568bc04d35e5de3eb2ee8c15167
Merge "Convert hardware.VirtCPUTopology to nova object"