Gavin Newsom, the governor of California, met with China’s leader, Xi Jinping, in Beijing on Wednesday, according to the Chinese state media, as part of an ambitious weeklong mission to negotiate climate partnerships. The two-term Democratic governor wants California to set an aggressive pace for the United States — and the world — to cut carbon emissions that are dangerously heating the planet. Mr. Newsom’s moves to tackle the climate crisis have elevated his national profile, just as he is widely believed to be preparing for a White House run…