MINOR: cpu-topo: consider capacity when forming clusters

MINOR: cpu-topo: consider capacity when forming clusters

By using the cluster+capacity sorting function we can detect
heterogneous clusters which are not properly reported. Thanks to this,
the following misnumbered machine featuring 4 big cores, 4 medium ones
an 4 small ones is properly detected with its clusters correctly
assigned:

      [keep] thr=  0 -> cpu=  0 pk=00 no=00 cl=000 ts=000 capa=1024
      [keep] thr=  1 -> cpu=  1 pk=00 no=00 cl=002 ts=008 capa=278
      [keep] thr=  2 -> cpu=  2 pk=00 no=00 cl=002 ts=009 capa=278
      [keep] thr=  3 -> cpu=  3 pk=00 no=00 cl=002 ts=010 capa=278
      [keep] thr=  4 -> cpu=  4 pk=00 no=00 cl=002 ts=011 capa=278
      [keep] thr=  5 -> cpu=  5 pk=00 no=00 cl=001 ts=004 capa=905
      [keep] thr=  6 -> cpu=  6 pk=00 no=00 cl=001 ts=005 capa=905
      [keep] thr=  7 -> cpu=  7 pk=00 no=00 cl=001 ts=006 capa=866
      [keep] thr=  8 -> cpu=  8 pk=00 no=00 cl=001 ts=007 capa=866
      [keep] thr=  9 -> cpu=  9 pk=00 no=00 cl=000 ts=001 capa=984
      [keep] thr= 10 -> cpu= 10 pk=00 no=00 cl=000 ts=002 capa=984
      [keep] thr= 11 -> cpu= 11 pk=00 no=00 cl=000 ts=003 capa=1024

Also this has the benefit of always assigning highest performance
clusters with the smallest IDs so that simple configs can decide to
simply bind to cluster 0 or clusters 0,1 and benefit from optimal
performance.