Wealthy Angelenos are trading their sprawling mansions for deluxe apartments in the sky. These days, Los Angeles developers are betting big on a flashy class of multimillion-dollar residences. Towering new condos are positioned to draw buyers away from the city’s traditional stock of hilltop mansions — and the biggest names in ultra-luxury hospitality, like Rosewood, Aman and Mandarin Oriental, are in on the action. A mammoth project underway across 17.5 acres of Beverly Hills sits at the trend’