Reduce duplication in Huddle spec

When we introduced huddle, we only reduced duplication for definitions that are exactly the same between eras. But, huddle is a lot more powerful than that, since it has the full power of Haskell and we can be much smarter about how we reuse huddle spec from previous eras. 

This is a task to go through all the eras and change the huddle spec to reduce duplication as much as possible.