Vanessa Kirby, who played Princess Margaret on the first two seasons of Netflix’s “The Crown,” has returned to the streaming service in the ac­quisition “Pieces of a Woman.” In the Kornél Mundruczó film, Kirby plays Martha, whose home birth ends in tragedy, upending her life. The birth scene, early in the movie, is a harrow­­ing 24-minute single take, based on the experience of “Pieces of a Woman” screenwriter Kata Wéber (and her partner, Mundruczó). For Amanda Seyfried, whose first film role was Karen in “Mean Girls,” David Fincher’s “Mank” (also on Netflix) was “a dream come true, actually.” In “Mank,” Seyfried’s Marion Davies forges a warm bond with Gary Oldman’s Herman Mankie­wicz — but that won’t stop him from betraying her as he writes “Citizen Kane.”