MINOR: cpu-topo: add a new "resource" cpu-policy

MINOR: cpu-topo: add a new "resource" cpu-policy

This cpu policy keeps the smallest CPU cluster. This can
be used to limit the resource usage to the strict minimum
that still delivers decent performance, for example to
try to further reduce power consumption or minimize the
number of cores needed on some rented systems for a
sidecar setup, in order to scale the system down more
easily. Note that if a single cluster is present, it
will still be fully used.

When started on a 64-core EPYC gen3, it uses only one CCX
with 8 cores and 16 threads, all in the same group.