Every once in a while, Hollywood gets high on its own supply and makes a love letter to moviemaking. It happened recently with Steven Spielberg’s “The Fabelmans” and George Clooney’s “Jay Kelly.” Now it’s time for the unlikeliest of love-letter writers: canary-yellow, gibberish-speaking, overall-wearing mini-monsters. “Minions & Monsters” — the third chapter in the ongoing standalone adventures of the “Despicable Me” pint-sized enablers — is about the sheer greatness of moviemaking, and it’s a