Add support for multi-die packages

[connorimes]

Newer Cascade Lake AP processors support multiple die on a package (socket) [1, 2]. Adding support will require new functions that accept die parameters to correctly identify which RAPL MSR or powercap (sysfs) parent zone to use.

[1] https://lkml.org/lkml/2019/5/13/768
[2] https://en.wikichip.org/wiki/intel/microarchitectures/cascade_lake

This work is already in progress, but this issue is to more publicly track the interface changes.