[14] RFR (S) 8240749: Shenandoah: refactor ShenandoahUtils

[Aleksey Shipilev]

Original change:
  https://bugs.openjdk.java.net/browse/JDK-8240749
  https://hg.openjdk.java.net/jdk/jdk/rev/a74b7501917d

It has a minor conflict due to missing JDK-8228818, so hunk in shenandoahHeap.cpp does not have
associated phase_timings changes. I moved the ShenandoahGCPhase to the same place, though.

14u webrev:
  https://cr.openjdk.java.net/~shade/8240749/webrev.14u.01/

Testing: hotspot_gc_shenandoah

-- 
Thanks,
-Aleksey