Reviewed-by: mgerdin, coleenp

Summary: Stack allocate instances of HeapRegionRemSetIterator during RSet scanning.
Reviewed-by: brutisso, jwilhelm

Summary: Restructure initialization of ClassLoaderData to not add a new instance if init_dependencies fail
Reviewed-by: stefank, coleenp

Reviewed-by: johnc, brutisso, stefank

Reviewed-by: tschatzl, jmasa

Reviewed-by: jcoomes