[14] RFR (S) 8244732: Shenandoah: move heuristics code to gc/shenandoah/heuristics

[Aleksey Shipilev]

Original RFE:
  https://bugs.openjdk.java.net/browse/JDK-8244732
  https://hg.openjdk.java.net/jdk/jdk/rev/1c6c963683e2

Context is a bit different, so I re-made the actual moves, and applied the rest of the hunks
automatically. 14u webrev:
  https://cr.openjdk.java.net/~shade/8244732/webrev.14u.01/

Testing: hotspot_gc_shenandoah {fastdebug,release}

-- 
Thanks,
-Aleksey