It was the question on many a tongue, in supermarket parking lots, in coffee shops, among fishermen and their lobster pots: After a ticket purchased in a Stop & Shop here hit the Powerball jackpot, the question that had Newport abuzz was this: “What would you buy with 336.4 million bucks?’’ But in a town famous as the playground for wealthy seafarers, that question rendered modest answers attesting to the reality that Newport is home to many of modest means.