Arguably Stephen Sondheim’s masterpiece (personally, I’m equally smitten with “Sunday in the Park With George”), with a book by Hugh Wheeler, “Sweeney” is a feast for the eyes, ears and heart. The show has proved sufficiently strong to work in various formats, from fully staged productions, to scaled-down versions with musicians doubling as the actors, to semi-staged productions such as the one opening the 40th season of “Live From Lincoln Center” on Friday on PBS. Lonny Price, who semi-staged “Sweeney” for the New York Philharmonic and the San Francisco Symphony 14 years ago, works his magic again with this Lincoln Center production, managing to make viewers all but forget the presence of a symphony orchestra sharing the stage with a murderous barber and his giddily unhinged abettor, Mrs.