It has been a long time since David Bowie has felt this good about himself. The former David Robert Jones, Ziggy Stardust and Thin White Duke has carved out a new musical niche without creating a new persona to play it out. Bowie is in Liverpool, England, on this day, congenially promoting his group, Tin Machine. He’s newly engaged to the model Iman, and sips on a cup of hot tea, his substance of choice these days. Mentally scanning his flamboyant 25-year career, he comes to the conclusion that his life, as that of most musicians, would make a boring film.