[14] RFR (M) 8242082: Shenandoah: Purge Traversal mode

[Aleksey Shipilev]

Original fix:
  https://bugs.openjdk.java.net/browse/JDK-8242082
  https://hg.openjdk.java.net/jdk/jdk/rev/d8d2145c205c

The context is quite different due to missing Traversal-related backports. Otherwise it is pretty
straightforward.

14u webrev:
  https://cr.openjdk.java.net/~shade/8242082/webrev.14u.01/

Testing: hotspot_gc_shenandoah, tier{1,2,3} with Shenandoah

-- 
Thanks,
-Aleksey