The fourth season of Amazon Prime’s “Reacher,” adapted from Lee Child’s Jack Reacher novels, finds our hulking hero (Alan Ritchson) ensnared in a government conspiracy in Philadelphia, all while trying to get his hands on a cheesesteak. “People keep telling me to mind my business,” he dryly observes, with the CIA and a small army of assassins on his tail. The season begins with Reacher intervening when he suspects a woman aboard the subway may b…