LOS ANGELES — Red-carpet premieres are the pinnacle of any new Hollywood blockbuster’s publicity blitz. Their A-list entourages, elbow-to-elbow fans and showbiz photographers vying for the perfect snaps of glamorous stars, are also a nightmare for social distancing. But with California coronavirus restrictions easing, and major movies like “Tenet” eyeing July release dates, Tinseltown’s marketing gurus are scrambling for ways to safely roll out those carpets once again.