qemu: monitor: Add algorithm for combining query-(hotpluggable-)-cpus data

qemu: monitor: Add algorithm for combining query-(hotpluggable-)-cpus data

For hotplug purposes it's necessary to retrieve data using
query-hotpluggable-cpus while the old query-cpus API report thread IDs
and order of hotplug.

This patch adds code that merges the data using a rather non-trivial
algorithm and fills the data to the qemuMonitorCPUInfo structure for
adding to appropriate place in the domain definition.