HANOI — When he vowed to “solve” the North Korea problem just before his inauguration two years ago, President Trump made clear he meant eliminating its nuclear arsenal. But on the eve of a second meeting with the North Korean leader, Kim Jong-un, the president sounds prepared to accept much less, at least for the foreseeable future. “I don’t want to rush anybody,” he said this past weekend. “As long as there is no testing, we’re happy,” he added, pointing to the North’s suspension of nuclear and missile tests. Even to some of Mr. Trump’s national security aides, that sounded like a significant retreat at a critical moment. As he landed in Hanoi late Tuesday, Mr. Trump appeared determined to change America’s relationship with a nation that has been a bitter and brutal adversary for nearly 70 years — and willing to shift his administration’s goals to do so, from immediate dismantlement of the North’s arsenal to limits on its size and reach. It is unclear whether the two men will emerge in the coming days with any of the breakthroughs that appear in the mix for discussion: a freeze on nuclear production, a peace agreement aimed at formally ending…