WEST PALM BEACH, Fla. — Did baseball’s best current rivalry hold a dress rehearsal Thursday at The Ballpark of the Palm Beaches? No, Mets-Nationals can’t hold a finger to Yankees-Red Sox, Dodgers-Giants or Cardinals-Cubs when it comes to history and regalness. In 2017, though? Mets-Nationals has two critical attributes going for it: 1) It’s close....