lib/group_cpus: make group CPU cluster aware

[Guo, Wangyang]

> We see its not the case, before this patch, irqs smp_allowed_list was sequential, but after the patch this changes.
> I think this has to do with cache locality effects, when tasks run on "wrong" CPUs. If you want us to check perf data, we can run that.

Nice catch. However, if this is indeed a cache locality issue, I would expect the performance impact to be more consistent. 
The results show a 4% performance improvement at jobs=32, which seems to contradict that explanation.

> Below patch[1] fixes the issue for us. Basically keep the cpu order if resources are equal, meanwhile keeping the benefit of your patches for clustering.

Yes, this is related to stable sorting, such change can preserve the order.