Upon my return from a weekend in New York City, I reviewed three Big Apple musicals in last week’s column. But there’s one more that I want to share. With the subject being the Holocaust, its mood is somber but the play is thoughtful and provocative.Sir Tom Stoppard — one of the world’s greatest writers for film, television and stage with works that include “Rosencrantz and Guildenstern are Dead,” “Jumpers” and “The Coast of Utopia” — recently wrote “Leopoldstadt,” which premiered on Broadway in 2020.This magnum opus …