FOSSE/VERDON isn’t about Broadway, but an impressionistic, absorbing take on life as art and art as life, told like a fragmented sensory puzzle — Yes, I know, I’m being evil. One singular sensation is the opening line from One, a song from A Chorus Line, the musical that opened opposite Chicago in the mid-seventies Broadway, out-earned it, out-Tony-ed it and out-ran it. Maybe a better title should have been All That Jazz — but…