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

[Roland Westrelin]

Thanks for looking at this, Tobias.

> Just wondering, is it possible that only after parsing we figure out that the exact type of the
> allocation is not a value type (or a flattened value type)?

It's possible. The problem then is that
GraphKit::initialize_value_type_array() is only called if we know the
exact type at parse time. Once we have parsed that allocation, then we
would only be able to clear is_unknown_value if we emitted the
allocation code from GraphKit::initialize_value_type_array() as well.

Roland.