It is one of Woody Allen's finest films, a screwball thriller written and shot as he battled Mia Farrow in court and faced accusations of child abuse. As Bullets Over Broadway hits the stage, Peter Bradshaw examines how the director's personal traumas fed into the storyHe's back. But then he was never away. Woody Allen, still battered with controversy from the Dylan Farrow allegations, still enjoying a residual glow…