[8] 2019-10-29: Bulk backports to sh/jdk8

[Roman Kennke]

Ok. Thanks!

Roman


> https://cr.openjdk.java.net/~shade/shenandoah/backports/jdk8u-20191029/webrev.01/
> 
> This batch brings in a few simple backports to sh/jdk8, in preparation for x86_32 backporting work
> and exposing sh/jdk8 to wider testing. I carefully selected backports that do not clash with
> Traversal and/or larger changesets.
> 
> Changes:
>  [backport] 8223450: Disable Shenandoah C2 barriers verification for x86_32
>  [backport] 8224881: Shenandoah: trashing "Collection Set, Pinned" region during Degenerated GC
>  [backport] 8231946: Remove obsolete and unused ShenandoahVerifyObjectEquals flag
>  [backport] 8225229: Shenandoah: trim down default number of GC threads
>  [backport] 8231932: Shenandoah: conc/par GC threads ergonomics overrides user settings
>  [backport] 8226957: Shenandoah: Remove obsoleted ShenandoahStoreCheck option
>  [backport] 8232702: Shenandoah: gc/shenandoah/TestVerifyJCStress.java uses non-existent
> -XX:+VerifyObjectEquals
>  [backport] 8225017: [TESTBUG] gc/shenandoah/oom/TestThreadFailure.java takes too long
> 
> Testing: hotspot_gc_shenandoah {fastdebug,release}
>