PONTIAC, Michigan — General Motors Co. may be relentlessly promoting an electric future with its sleek-looking EVs for retail customers, but for decades the automaker also has been developing hydrogen fuel cell propulsion technology — and now it’s ready to start making money from it. The movement to commercialization starts with the Hydrotec fuel cell lab and work areas in Pontiac that are three football fields large and neighbor other propulsion operations. It’s here where teams collaborate to improve the technology that will be used to power larger modes of transportation from semis to train…