Ethel Merman. Angela Lansbury. Bernadette Peters. Patti LuPone. Imelda Staunton. One name, pretty clearly, doesn't belong on that list of larger-than-life musical comedy stars--and, thus, seems an unlikely candidate for the larger-than-life role of Rose in Gypsy. But that distinction is the key to what makes the current West End Gypsy, at the Savoy, so indomitable.