[15] RFR 8245823: Shenandoah: inline/optimize ShenandoahEvacOOMScope

[Zhengyu Gu]

Please review this patch that makes ShenandoahEvacOOMScope inline-able, 
also avoids calling ShenandoahHeap::heap() and Thread::current() if 
caller can provide them.

The gain is not as noticeable as JDK-8245240 and JDK-8245288, but seems 
consistent.


Bug: https://bugs.openjdk.java.net/browse/JDK-8245823
Webrev: http://cr.openjdk.java.net/~zgu/JDK-8245823/webrev.00/index.html

Test:
   hotspot_gc_shenandoah

Thanks,

-Zhengyu