[11] RFR: 2019-10-24, bulk backports to sh/jdk11

[Aleksey Shipilev]

https://cr.openjdk.java.net/~shade/shenandoah/backports/jdk11-20191024/webrev.01/

This bunch includes:

 [backport] 8232205: Shenandoah: missing "Update References" -> "Update Roots" tracing
 [backport] 8232534: Shenandoah: guard against reentrant ShenandoahHeapLock locking
 [backport] 8232573: Shenandoah: cleanup and add more logging for in-pause phases
 [backport] 8232575: Shenandoah: asynchronous object/region pinning
 [backport] 8232802: Shenandoah: transition between "cset" and "pinned_cset" does not require
cancelled gc
 [backport] 8232702: Shenandoah: gc/shenandoah/TestVerifyJCStress.java uses non-existent
-XX:+VerifyObjectEquals
 [backport] 8232730: Shenandoah: Traversal should not CAS the roots
 [backport] 8232729: Shenandoah: assert ShenandoahHeap::cas_oop addresses are aligned
 [backport] 8232791: Shenandoah: passive mode should disable pacing
 [backport] 8232908: Shenandoah: compact heuristics has incorrect trigger "Free is lower than
allocated recently"

Testing: it passed a few nightlies in jdk/jdk; hotspot_gc_shenandoah {fastdebug, release}

-- 
Thanks,
-Aleksey