It might be the biggest party this small west Indian city has ever seen. Billionaire Mukesh Ambani is kickstarting big fat Indian wedding celebrations for his son, Anant Ambani, 28, who is set to marry his longtime girlfriend Radhika Merchant. He’s expecting billionaires from around the world, heads of state, and Hollywood and Bollywood royalty to attend a three-day bash in the family’s hometown, which kicked off on Friday. The occasion that has India transfixed is a three-day pre-wedding jamboree for his youngest son…