WASHINGTON — President-elect Donald J. Trump has selected Senator Jeff Sessions, a conservative from Alabama who became a close adviser after endorsing him early in his campaign, to be the attorney general of the United States, according to officials close to the transition. Mr. Sessions was also under consideration for secretary of defense, creating debate within the Trump transition team over which job he should fill. Mr. Sessions, a former prosecutor elected to the Senate in 1996, serves on the Judiciary Committee and has opposed immigration reform as well as bipartisan proposals to cut mandatory minimum prison sentences...