If Norma Desmond were a real person, and were she still with us, she’d be jumping for joy right about now. That’s because the fictional Hollywood has-been at the center of “Sunset Boulevard” — first introduced by a garishly made-up, 50-ish Gloria Swanson in Billy Wilder’s satirical film noir — is now being played on Broadway by Nicole Scherzinger, the drop-dead-gorgeous singer and actress who rose to fame as a member of a girl group, The Pussycat Dolls.