[11] 2020-05-12, Bulk backports to sh/jdk11

[Aleksey Shipilev]

https://cr.openjdk.java.net/~shade/shenandoah/backports/jdk11-20200512/webrev.01/

This backports logging improvements to sh/jdk11. Not all patches apply cleanly, so please review
carefully.

Changesets:
 [backport] 8241984: Shenandoah: enhance GCTimer and JFR support
 [backport] 8242375: Shenandoah: Remove ShenandoahHeuristic::record_gc_start/end methods
 [backport] 8242400: Shenandoah: Restore logging to pre-jdk8241984 format
 [backport] 8242625: Shenandoah: restore heap logging for Degenerated/Full cycles
 [backport] 8242638: Shenandoah: restore heap logging for uncommit
 [backport] 8243487: Shenandoah: make _num_phases illegal phase type
 [backport] 8243494: Shenandoah: set counters once per cycle
 [backport] 8239786: Shenandoah: print per-cycle statistics
 [backport] 8243848: Shenandoah: Windows build fails after JDK-8239786
 [backport] 8243573: Shenandoah: rename GCParPhases and related code
 [backport] 8243578: Shenandoah: Cleanup ShenandoahStringDedup::parallel_oops_do()
 [backport] 8244180: Shenandoah: carry Phase to ShWorkerTimingsTracker explicitly
 [backport] 8244226: Shenandoah: per-cycle statistics contain worker data from previous cycles
 [backport] 8244326: Shenandoah: global statistics should not accept bogus samples

Testing: hotspot_gc_shenandoah {fastdebug,release}, tier{1,2} with Shenandoah, eyeballing gc logs

-- 
Thanks,
-Aleksey