numa: fix cpu topology conversion for non linux systems

[shoenig]

The linux path is unchanged (just moved into _linux file). The non-linux path now no longer references dead / unusable fields on non-linux systems.

E.g. is meaningless outside of Linux.

cores := n.Processors.Topology.UsableCores().Slice()
n.Cpu.ReservableCpuCores = helper.ConvertSlice(cores, func(coreID hw.CoreID) uint16 {
	return uint16(coreID)
})

Also fixes the use of "power" where we meant "performance" in reference to M1/M2 P-Cores in the attributes.

[tgross]

LGTM!

Thanks for the pointers on the file moves... it makes it easier to review side-by-side 😀