Several characters in “ Decorado ” are on the brink of a mental breakdown. Poverty, unemployment and a constant state of paranoia have driven them to feel like they are trapped inside an artificial set, where every element in their lives feels fake and orchestrated by an ominpresent Big Brother-like business known as ALMA (Almighty Limitless Megacorporative Agency). And their suspicions might not be unfounded. Following “Birdboy: The Forgotten Children” and “Unicorn Wars,” the third feature from Spanish director Alberto Vázquez (all three of them have won the Goya Award for Best Animated Film) is an expansion of his 2016 short film, also titled “Decorado” (which earned him another Goya). Like its gruesome predecessors, his latest full-length work features adorably designed anthropomorphic animals (and mushrooms) navigating bleak realities and confronting existentialist concerns.…