RFR 8223774: Shenandoah: Refactor ShenandoahRootProcessor and family

[Zhengyu Gu]

>>
> 
> But you can put the line:
> 
> FLAG_SET_DEFAULT(ShenandoahConcurrentScanCodeRoots, false);
> 
> in the constructor of the ShenandoahTraversalHeuristics, together with
> other similar lines.
Ah, I misunderstood.

Updated: http://cr.openjdk.java.net/~zgu/JDK-8223774/webrev.02/

-Zhengyu

> 
> Roman
> 
>