LAS VEGAS — Sin City said goodbye to the Tropicana in an elaborate implosion that leveled two hotel towers. The celebration in Las Vegas early Wednesday included a fireworks display. It was the first casino implosions in nearly a decade for a city that loves fresh starts. The Tropicana closed in April after 67 years to make room for a new baseball stadium for the relocating Oakland Athletics. Once known as the “Tiffany of the Strip” for its opulence, the Tropicana was a frequent haunt of the legendary Rat Pack. Its past under the mob has long cemented its place in Las Vegas lore.