RFR: Rename fields in (SA) ShenandoahHeap.java to omit 'Regions' and 'Field' suffix

[Aleksey Shipilev]

On 11/30/18 1:30 PM, Roman Kennke wrote:
> ... makes field naming consistent and less misleading (it is *not* the
> number of used vs. committed regions).
> 
> Testing: tier1_gc_shenandoah (should be a compile-time-issue only)

There's no webrev in this RFR, but I believe it is a clean dissect from the previous RFR?

-Aleksey