For a show as deliriously playful as “Irma Vep,” the HBO limited series created, written and directed by the French filmmaker Olivier Assayas, its deepest truths are often the most bluntly spoken. One speaker is Mira Harberg (Alicia Vikander), a Hollywood star who’s playing the Parisian jewel thief Irma Vep in a remake of “Les Vampires,” Louis Feuillade’s 1915 crime serial. Enjoying a free moment with another actor, Cynthia (Fala Chen), Mira quietly extols the power of cinema and laments its growing obsolescence in a content-saturated era: “Movies are a portal to some sort of spiritual world w…