RFR(M): arraycopy/clone/copyOf intrinsics fixes for Lworld

[Roland Westrelin]

> But we don't need that code if the array turns out to be not a value type array, right? And also,
> GraphKit::initialize_value_type_array() does not allocate but just load the default oop.
>
> My point was that we could then omit the runtime checks in macro.cpp that are guarded by
> is_unknown_value().

Ah! you're right. I will make that change.

Roland.