RFR(M): 8206141: [lworld] Improve accessing a flattened value type array passed as Object[]

[Roland Westrelin]

Hi Tobias,

Thanks for reviewing this.

> I've submitted some testing and I'm hitting "assert(_base == AryPtr) failed: Not an array pointer"
> with vmTestbase/vm/mlvm/indy/stress/java/loopsAndThreads/TestDescription.java and
> -XX:+EnableValhalla (see stack trace below).

I can't reproduce that one with. Was there a replay file?

Roland.