“X -Men: Apocalypse” is a veritable pinata of mutants, a picturesque eruption of the world as we know it – or at least as comic book fans do – scattering trails of smoke, rubble, dead bodies and genetically enhanced superheroes every which way. With a main cast of 20, including four unnamed mutants who are quickly dispatched during a prologue in ancient Egypt, the latest sequel in the beloved Marvel Comics movie saga about freaks of nature is, even by today’s bloated standards of the genre, a bit overstuffed.