It didn’t matter that Marisa Abela doesn’t really look like Amy Winehouse, the lauded British vocalist she plays in the new biopic “Back to Black.” As the first actress to audition for Sam Taylor-Johnson — and the only one not to arrive dressed as Winehouse — she stunned the director from the get-go. Taylor-Johnson recalls grabbing casting director Nina Gold’s hand after observing a “seismic shift” in Abela’s demeanor as she began to read for a camera test. She didn’t need to rely on a resemblance.