RFR (M) 8244180: Shenandoah: carry Phase to ShWorkerTimingsTracker explicitly

[Aleksey Shipilev]

Original RFE:
  https://bugs.openjdk.java.net/browse/JDK-8244180
  https://hg.openjdk.java.net/jdk/jdk/rev/649dbd90e0e9

This is a part of bulk backport of enhanced Shenandoah logging to 14u. Again, the context is a bit
different, because weak/strong roots split is not there.

14u webrev:
  https://cr.openjdk.java.net/~shade/8244180/webrev.14u.01/

Testing: hotspot_gc_shenandoah, eyeballing gc logs

-- 
Thanks,
-Aleksey