ART: Allow array-ness for unresolved merge types

In case component types aren't resolvable, array types won't be
either. They then may be merged. The merge is still potentially
an array type.

Ensure that merging an unresolved array type with a primitive
array type or a non-array type will be resolved to java.lang.Object.

Added tests.

Bug: 27799205
Change-Id: I9beff75318814dddd842abd64ef9a5d2644d801e