JUPITER, Fla. — The news was music to Garrett Cooper’s ears. The designated hitter is in the National League full-time as part of the new collective bargaining agreement after being a temporary measure during the pandemic-shortened 2020 season. The hit-first, defense-second Cooper was a big endorser of the designated hitter becoming permanent last year, but MLB opted to revert back to the normal lineup in 2021 — pitchers hitting in the National League, the designated hitter only in the American League. “I think MLB messed up,” Cooper said then. Now? He’s happy. The Marlins overall are, too, es…