At the core of “Carousel,” which has been revived with breathtaking emotional intensity at the Imperial Theatre, is a dark fatalism that trails the leading lovers like their own shadows. Although the major Rodgers & Hammerstein musicals are broadly considered, with good reason, to be shot through with romance and uplift, in this 1945 musical — their greatest, in my view — they explored the facets of love and of life that bring as much sadness and sorrow as pleasure and joy. The new production, Broadway’s first since Nicholas Hytner’s landmark 1994 revival, has been directed by the veteran Jack…