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

[Aleksey Shipilev]

RFE:
  https://bugs.openjdk.java.net/browse/JDK-8244180

See the rationale in JIRA: it blocks JDK-8243495 (and other counter work, like class unloading).

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

Testing: hotspot_gc_shenandoah, tier{1,2,3} with Shenandoah; tests with JDK-8243495 (where the issue
was discovered)

-- 
Thanks,
-Aleksey