It’s the Fourth of July in “The Last Day,” and the weather is playing ball: the kind of soft, slouchy summer heat made for a leafy garden party. But a chill runs through Rachel Rose ‘s elegantly restrained, internalized character study. It crisps the edges of the film’s immaculately lit frames and causing its two principal characters, tautly played by Alicia Vikander and Victoria Pedretti , to stiffen slightly, unable to give themselves over to the day’s balmy mood. Both are mothers, and