THE MAN on stage with the bulging barfly beard and ruffled scraps of remaining hair may not look much like royalty. But Bonnie "Prince" Billy, aka Will Oldham, is certainly among the aristocracy of the burgeoning movement of introspective, traditionally rooted bands that currently form white America's main resistance to the cultural mainstream. Sometimes misleadingly named alt.country, Oldham has been more than its prince, ever since he put child film stardom behind him to form his first band, Palace Brothers, in 1993. With albums such as 1999's I See a Darkness, he has been dubbed the genre's King of Pain. His solo gigs are similarly supposed to be bleak, intense affairs, not …