SANTA MONICA, California — One is a living legend in music and movies, the other is a living legend about to make her movie debut. Now, Cher and Christina Aguilera are being joined by a red-hot “Twilight” star who will be appearing in his first musical opposite the two famous females: Cam Gigandet.

“I’m shooting a movie called ‘Burlesque’ with Christina Aguilera in her acting debut,” Gigandet revealed when he stopped by the MTV studio recently. “And Cher.“
Xtina’s fans have been eager to learn details on “Burlesque” since the project was …