By Stephanie Apstein He never thought he would leave the Cubs. But he’s loving it (and slugging it!) in New York. Welcome to The Opener, where every weekday morning during the regular season you’ll get a fresh, topical story to start your day from one of SI.com’s MLB writers. NEW YORK — As Anthony Rizzo’s free agency stretched into its fifth month, he realized two things: After a disappointing 2020 and ’21, “the deal that I once envisioned wasn’t gonna be there,” he says. And if he couldn’t get five years, he didn’t want three. He wanted one. Rizzo has heard the same rumors as everyone else in…