LONDON — Lorenzo Musetti threw his head back and spread his arms wide to celebrate reaching his first Grand Slam semifinal at Wimbledon, then covered his face with both hands. “Jokes apart, he’s a legend everywhere, but especially here in Wimbledon.” This will be Djokovic’s record-tying 13th semifinal at Wimbledon alone — equaling Roger Federer — and 49th Slam semifinal …