[foreign] RFR 8220677: Panama API should support bulk array copy to and from Java arrays

[Maurizio Cimadamore]

Hi,
this patch generalizes the patch proposed and discussed in [1, 2].

I've generalized BoundedArray::copyFrom/To so that they can do bulk copy 
when possible, which will speed up Scope::allocateArray, Array::toArray 
and the newly added Array::assign methods.

Webrev:

http://cr.openjdk.java.net/~mcimadamore/panama/8220677/

Maurizio

[1] - 
https://mail.openjdk.java.net/pipermail/panama-dev/2019-March/004868.html
[2] - 
https://mail.openjdk.java.net/pipermail/panama-dev/2019-March/004842.html