WASHINGTON — U.S. hiring swelled in October by the largest amount all year, and unemployment dropped another notch to 5 percent, increasing the likelihood that the Federal Reserve will raise interest rates next month for the first time in a decade. With Americans spending more on everything from restaurant meals and clothing to new cars, employers added an impressive 271,000 jobs last month. That was a strong rebound from August and September, when turmoil in China and other economies overseas proved a drag on the U.S. job market.