Fairmount Park, the 95-year-old horse racing track that has been waiting years for new revenue from casino gambling and sports wagering, is embarking on a new partnership that promises to expand sports betting, reinvest in the property — and change its name. In the race to offer online sports betting under Illinois’ new wagering law, Fairmount Park is partnering with New York-based online sports wagering firm FanDuel Group and renaming itself FanDuel Sportsbook and Horse Racing.