ANN ARBOR, Mich. — That happened fast. Not just for Michigan, but for Sherrone Moore. Moore, who just seven years ago was coaching tight ends and running backs at Central Michigan, was officially introduced as the 21st head football coach of Michigan on Saturday. The announcement came Friday, just two days after Jim Harbaugh signed a contract to return to the NFL with the Los Angeles Chargers, after Harbaugh had led the Wolverines to the national championship. Moore is the first Black head coach in Michigan football history, and, at 37, he is the youngest head football coach at Michigan in mor…