From Richard Chamberlain on ‘Dr. Kildare’, to George Clooney on ‘ER’, television’s long love affair with doctors and nurses shows no signs of letting up. Noah Wyle, Anthony Edwards, Gloria Reuben and Eriq LaSalle open up about the secrets of ‘ER’; Howie Mandel, Ed Begley Jr. and Christina Pickles revisit ‘St. Elsewhere’.