Change broker request and response to use Seqs rather than Array

The new Produce and Fetch request and response classes use primitive Arrays, but becaue they are case classes and Java's array hashCode/equals functionality is broken, the case class equality contract is broken as well. We should change the models to use Seqs to resolve the issue along with gaining all the functional benefits that goes along with it. This change will require appropriate Java versions to convert between Array's and Seqs for Java clients.