By Nathan Layne, Gram Slattery and James Oliphant MANCHESTER, New Hampshire (Reuters) -Donald Trump cruised to victory in New Hampshire’s Republican presidential contest on Tuesday, marching closer to a November rematch with Democratic President Joe Biden even as his only remaining rival, former U.N. Ambassador Nikki Haley, vowed to soldier on. “This race is far from over,” she told supporters at a post-election party in Concord, challenging Trump to debate her. “I’m a fighter. And I’m scrappy. And now we’re the last one standing next to Donald Trump.” At his own party in Nashua, Trump opened …