MOSCOW/LONDON (Reuters) – Some of the world’s most powerful oil executives will attend Russia’s top investment show next week, once again helping the organizers shrug off a meager turnout from other leading Western industrialists and bankers. Many CEOs and chairmen from major U.S. and European firms withdrew from last year’s St Petersburg International Economic Forum because of tensions tied to Russia’s annexation of Crimea and a separatist war in eastern Ukraine.