RFR: Rename and cleanup _regions and _free_set uses

[Zhengyu Gu]

Good to me.

-Zhengyu

On 03/20/2018 08:35 AM, Aleksey Shipilev wrote:
> http://cr.openjdk.java.net/~shade/shenandoah/rename-or-fs/webrev.01/
> 
> Before we go and do more FreeSet work, we need to make a few cosmetic fixes:
>   *) Drop "active_regions" from everywhere. It stopped making sense after we did heap uncommit
> mechanics, which made all regions available in the region set at all times;
>   *) "ordered_regions" name is too verbose, of course they are ordered;
>   *) "num_regions()" and "capacity()" are used where applicable, without polling the region set
> 
> Testing: hotspot_gc_shenandoah
> 
> Thanks,
> -Aleksey
> 
>