[8] RFR: 2020-05-19, Bulk backports to sh/jdk8

[rkennke at redhat.com]

Looks good, thank you!

Roman


> https://cr.openjdk.java.net/~shade/shenandoah/backports/jdk8u-20200519/webrev.01/
> 
> This backports a few easy leftovers, mostly file moves to sh/jdk8:
>  [backport] 8241062: Shenandoah: rich asserts trigger "empty
> statement" inspection
>  [backport] 8244730: Shenandoah:
> gc/shenandoah/options/TestHeuristicsUnlock.java should only verify
>  [backport] 8244732: Shenandoah: move heuristics code to
> gc/shenandoah/heuristics
>  [backport] 8244737: Shenandoah: move mode code to gc/shenandoah/mode
>  [backport] 8244739: Shenandoah: break superclass dependency on
> ShenandoahNormalMode
>  [backport] 8244740: Shenandoah: rename ShenandoahNormalMode to
> ShenandoahSATBMode
> 
> Testing: hotspot_gc_shenandoah {fastdebug,release}
>