ART: Better support for arraycopy in unstarted runtime

Extend the System.arraycopy() cutout in the unstarted runtime
to support arrays with differing component types.

Add tests.

Bug: 27805718

(cherry picked from commit 85a098af)

Change-Id: Iaacd95a372e9bfa26e9055a06b0d8f0335b8d6d1