A new wave of billionaires is moving to Miami , but the neighborhoods they're calling home might not be the first that come to mind. Amid the wealth migration to the city — in part driven by  tax proposals  targeting the ultrawealthy — the leafy neighborhood of Coconut Grove has emerged as one of the most coveted addresses in South Florida. While some ultrawealthy new residents, like Jeff Bezos and Mark Zuckerberg, have gravitated toward private islands like Indian Creek Village or Fisher