Improve affinity integration.

 - Polish the non-affinity push/select
 - Setup basic affinity select (only cores)
 - Setup affinity push (thread/node/data/default)
 - Remove Kaapi's affinity: no need for it anymore!

Note: right now it's still possible to end up with a deadlock if affinity(node:X) is used, we don't visit the nodes' queue yet!
Next commit will introduce this.