By THÉRÈSE MARGOLIS      Ever since it first opened its doors inside the Presidente InterContinental Hotel in the capital city’s upscale Colonia Polanco back in 1996, Alfredo di Roma has been a mainstay of fine Italian dining in Mexico. Renowned for its incomparable fettuccine all’Alfredo (after all, the recipe was first created by Alfredo Di Lelio in the restaurant