On some summer afternoons between conference calls at the office, Anthony J. O’Neill will run upstairs, find an empty seat and catch a few innings of a White Sox game.O’Neill is general counsel for the Illinois Sports Facilities Authority, the government agency that serves as owner and developer of the ballpark now named Guaranteed Rate Field — more widely remembered as U.S. Cellular Field or New Comiskey Park. ISFA is also the financing authority for the Chicago Park District-owned Soldier Field.The past …