RFR: Unclutter ShConcurrentMark (multiple changes)

[Roman Kennke]

Looks good. Thanks!
Roman


> http://cr.openjdk.java.net/~shade/shenandoah/unclutter-scm/webrev.01/
> 
> This cleans up ShenandoahConcurrentMark interface a bit. Before doing it, there are a few cleanup
> patches that reduce its API surface.
> 
>  *) "Handle update_refs, class_unload, ref_proc in ShConcMark better": Inlines getters right at
> uses, since ShHeap instance is accessible anyway. Also improves mark_loop signatures without
> dragging these parameters along.
> 
>  *) "Common liveness cache in ShHeap": both ShConcurrentMark and ShTraversalGC use parts of the
> cache. Moreover, Traversal instantiates the array twice: once is ShConcurrentMark that it delegates
> marking to, and the second time for itself. It seems cleaner to common this caching in ShHeap.
> 
>  *) "Inline/rename confusingly named methods in ShConcurrentMark": make sure we have clear entry
> points that are shared by both concurrent and Full GC cycle;
> 
>  *) "Sort ShenandoahConcurrentMark methods/fields into logical groups": the final touch that
> reshuffles the methods around
> 
> Testing: tier3_gc_shenandoah {fastdebug|release}
> 
> Thanks,
> -Aleksey
>