[8] 2019-10-30: Bulk backports to sh/jdk8

[Aleksey Shipilev]

https://cr.openjdk.java.net/~shade/shenandoah/backports/jdk8u-20191030/webrev.01/

This backports the follow-up LRB bugfixes and other performance improvements:

 [backport] 8231405: [Shenandoah] guarantee(d != NULL) failed: Null dominator info
 [backport] 8229707: [TESTBUG] Some Shenandoah tests assume Server VM by default
 [backport] 8229350: Shenandoah does not need barriers before CreateEx
 [backport] 8225046: Shenandoah metrics logs refactoring
 [backport] 8231667: Shenandoah: Full GC should take empty regions into slices for compaction
 [backport] 8224932: Shenandoah: Rename ShenandoahHeapLock, make it general purpose lock
 [backport] 8229231: Shenandoah: Non-PCH builds failed after JDK-8224932
 [backport] 8232534: Shenandoah: guard against reentrant ShenandoahHeapLock locking
 [backport] 8232573: Shenandoah: cleanup and add more logging for in-pause phases
 [backport] 8231947: Shenandoah: cleanup ShenandoahHumongousMoves flag treatment
 [backport] 8232176: Shenandoah: new assert in ShenandoahEvacuationTask is too strong
 [backport] 8232575: Shenandoah: asynchronous object/region pinning
 [backport] 8232802: Shenandoah: transition between "cset" and "pinned_cset" does not require
cancelled gc

Testing: {x86_32, x86_64} x {fastdebug, release} hotspot_gc_shenandoah

-- 
Thanks,
-Aleksey