LONDON—British Prime Minister Boris Johnson said on Monday there is a choice coming soon on whether to mainline more Russian hydrocarbons or to back Ukraine, peace and stability, amid rising tensions between Moscow and the West. France and Germany on Monday warned Russia against harming Ukraine’s territorial integrity amid a large and unusual concentration of Russian troops on the country’s borders. As Europe experiences an energy crunch, Russian President Vladimir Putin is hoping German authorities will soon certify the Nord Stream 2 pipeline that will carry more Russian gas to Europe’s biggest economy. It would bypass transit countries, particularly Ukraine, which has a history of gas pricing standoffs with Moscow. “So when we say that we support the sovereignty and integrity of Ukraine, that is not because we want to be adversarial to Russia, or that we want in some way strategically to encircle or undermine that great country,” Johnson …