Kimi Antonelli is rapidly becoming one of the preeminent figures in Formula One. The 19-year-old Mercedes driver won his third race in a row at Sunday’s Miami Grand Prix , cementing himself as the championship front-runner in just his second season on the grid. And yet the second-youngest driver in the F1 paddock and the soon-to-be-if-not-already superstar of the sport seems wholly unaffected by it all.  Antonelli, who leads Mercedes teammate George Russell by 20 points atop the standings following the weekend in Miami, remains the only driver on the grid to stand on the podium in each of the four Grands Prix this season. But what happened in South Florida was different. For the first time this season, he was tested. A significant upgrade package from McLaren saw defending champion Lando Norris push Antonelli all weekend, and even beat him in Saturday’s sprint race.…