Test for the getArrayCopy method in AbstractRestultSet

If you're using the `ArraySerializable` hydrator, then you will have a method called `getArrayCopy` in your row object, However, `AbstractResultSet::toArray()`  currently checks that your row is an instance of `ArrayObject` and hence throws an exception. 

This PR changes `AbstractResultSet::toArray()` to check for the method name instead, to match the way that  `ArraySerializable::extract()` handles this.