By Paul Lienert and David Shepardson (Reuters) -General Motors Co said Tuesday it will invest $7 billion in Michigan, much of that aimed at dramatically boosting production of full-size electric pickups, intensifying a battle with rival Ford Motor Co for EV supremacy in North America. Both U.S. automakers, however, will have to contend with current leader Tesla, which will soon open a second U.S. plant in Austin, Texas, and is on pace to sell more than 1 million electric vehicles globally in 2022. GM said its Detroit-Hamtramck and Orion Township plants will be able to build more than 600,000 e…