Lionsgate has signed on Helen Mirren to star in “White Bird: A Wonder Story,” a spinoff of the hit 2017 inspirational film that starred Jacob Tremblay as a boy with a rare facial deformity.Also starring Gillian Anderson and directed by “Christopher Robin” filmmaker Marc Forster, “White Bird” sees “Wonder” cast member Bryce Gheisar return as Julian Albans, the antagonist of “Wonder” who bullied Auggie Pullman for his deformity and was suspended and later pulled from school by his mother — played