Uber has a new short-term car leasing partner for its drivers, and it’s none other than General Motors—a major investor in rival ride-hailing company Lyft. On Tuesday, Uber and a 10-month-old car-sharing division within GM announced a new pilot program in San Francisco that will let Uber drivers rent cars by the week for both work and personal use. As part of the 90 day test, drivers will be able to rent cars for $179…