Written by Choe Sang-Hun and Russell Goldman When outside intelligence officials seek evidence of North Korean leader Kim Jong Un leaving on a trip abroad — such as his journey to Russia this week to meet with President Vladimir Putin — they always look for the whereabouts of a train painted a drab green. This Sunday, Sept. 10, 2023, photo provided by the North Korean government, shows that North Korea leader Kim Jong Un greets attendants in Pyongyang, North Korea, before boarding on a train to Russia. (Korean Central News Agency/Korea News Service via AP) One such train was spotted...