Add missing decorators in calls to to arraycopy_prologue/epilogue

Calls to BarrierSetAssambler::arraycopy_prologue/epilogue() are missing the IN_HEAP and IN_HEAP_ARRAY access decorators. This is sort of ok, since the context (we're doing an arraycopy) imply these. However, by not explicitly specifying them we loose the ability to do straight forward checks/asserts on expected/allowed decorators later on in the GC specific BarrierSetAssermbler backends. To avoid having the backends know about this implicit relationship I propose that we explicitly specify them at the call-sites.