General Motors Co (NYSE: GM) CEO Mary Barra and Tesla Inc (NASDAQ: TSLA) Elon Musk revealed Thursday afternoon during a Twitter Spaces their companies' collaborative efforts toward a unified North American charging standard for electric vehicles. "This is the most exciting time when we look at this transformation to EVs," said Barra, who has more than 40 years of experience in the auto industry. Echoing Barra's sentiments, Musk said, "This is on…