Core power API in subcomponent simulation

[spolstra]

The default_subcomp branch contains the minimal changes to run a subcomponent simulation.
Core level power data is lost when running a subcomponent simulation as is show in this log snippet:

[Scheduler]: DVFS Control Loop invoked at 205.000.000 ns
[Scheduler][DVFS_MAX_FREQ]: Core  0: P=-1.000 W f=1000 MHz T=-1.0 °C utilization=0.000
[Scheduler][DVFS_MAX_FREQ]: Core  1: P=-1.000 W f=1000 MHz T=-1.0 °C utilization=0.376
[TRACE:1] -- DONE --

Add/fix the core level API so core metrics are shown correctly. The implementation would aggregate the subcomponent values for each core.