Knicks fans partied like it was 1999 on Monday night, punctuating a dominant run to the NBA Finals with a one-sided sweep of the Cleveland Cavaliers that plunged the Big Apple into jubilant chaos.   The win ended a 27-year dry spell since their last Finals appearance — and Knicks nation was quick to use the opportunity to make up for lost time. “The city has been waiting for it since 1999. We’ve been through so many losses and the fans have always stuck close. It’s nice to finally be on the