“Scene Partners,” which opened on Wednesday at the Vineyard Theater in a top-drawer production directed by Rachel Chavkin, is part of a genre you might call the absurd picaresque. Meryl is a hardheaded Candide, a sharp-eyed Don Quixote. When we meet her just after the long longed-for death of her abusive husband, she is leaving Wisconsin for California so fast she doesn’t bother burying him. “Within the year I will rise to fame and fortune as an international film star,” she says in farewell to her drug addict daughter. Sure enough, she soon acquires not just her agent and acting coach, but also a contract to write the movie of her life.