“I’ll figure it out.” Ethan Hunt’s reassurance, repeated through Mission: Impossible — Fallout, is the mantra of the eternal optimist, one embodied perfectly by Tom Cruise, contemporary blockbuster cinema’s most industrious instrument of can-do energy, only but one of the diligently-spinning cogs in Christopher McQuarrie’s meticulously constructed, if occasionally overwhelmed, return to the Impossible brand. If the traditional, Bondian image of espionage (pre-Daniel Craig anyway) is that of effortless ease — a silencer under a dinner suit, a wry one-liner with alcohol on the breath — then in Cruise we get the opposite: intelligence work as aerobic overkill. Under the instruction of the Impossible series’ five distinct directors (McQuarrie…