6664815: Eliminate redundant memcpy operation in jni_GetStringUTFRegion
Summary: Added support for target buffer in as_utf8_string(), minor refactoring of as_utf8 and added some internal VM testing
Reviewed-by: coleenp, dsimms, sla, dholmes
Contributed-by: marcus.larsson@oracle.com
8033405: metaspace/stressHierarchy/stressHierarchy005 hangs in atexit handler
Summary: <ake sure we shut down NMT before the VM exits and do not track malloc/free when NMT is shutting down
Reviewed-by: coleenp, zgu