+str #16077 implement Zip and friends for javadsl

This PR will contain more commits - for now it's just the Zip operation but wanted to show/get-early feedback on the method I used to not duplicate the implementation while being able to emit java Pairs or Tuple2s.  

Refs #16077
Yes, totally agree here - see my previous comment.
Will gladly fold in the match in here then :+1: