David Stearns took some big swings this offseason in making over the Mets roster, and a 12-game losing streak just two weeks into the year might lead an executive to some regrets. Stearns insisted Friday he remains confident in the group he put together as the president of baseball operations. “It’s tough for me to take two weeks — even two weeks when we didn’t win a baseball game — and say that’s going to dramatically alter who we think we are,’’ Stearns said before the Mets opened a series against the Rockies at Citi Field. “I still think we’re a good team,” Stearns said. “I recognize we had a stretch where we did not play good baseball, and it cost us. It cost us repeatedly.…