HIROSHIMA, Japan, May 21 (Reuters) - The Group of Seven (G7) rich nations signalled to Russia their readiness to stand by Ukraine for the long haul while giving President Volodymyr Zelenskiy a chance to win over countries such as Brazil and India on the last day of a summit in Japan. UKRAINE * Potential allied training programmes for Ukrainian pilots on F-16 warplanes were a message to Russia not to expect to succeed in its invasion of Ukraine even in a prolonged conflict, said German Chancellor Olaf Scholz. * President Joe Biden told G7 leaders that Washington supports the joint...