RFR: After GC reporting should also report metaspace progress

[Aleksey Shipilev]

On 09/25/2018 11:27 PM, Zhengyu Gu wrote:
> Following upstream discussion, Shenandoah should follow other GCs to report metaspace progress after
> GCs.
> 
> I also changed logging tag for heap from (gc, ergo) to (gc, heap) to be consistent with others.
> 
> Webrev: http://cr.openjdk.java.net/~zgu/shenandoah/metaspace_stats/webrev.00/

I am not OK with changing the tag to (gc, heap). Our adopters use those logging blocks to debug
ergonomics decisions, and it should stay (gc, ergo).

The logging seems to be better called from ShenandoahControlThread::run_service, that actually
drives the cycle. There is "if (gc_requested) ..." block that handles whatever actions that should
happen after the GC. Put the field tracking "last" metaspace usage in ShHeap, and call into ShHeap
from ShControlThread.

-Aleksey