The White House is considering options for leaving about 500 U.S. troops in northeast Syria and for sending dozens of battle tanks and other equipment, officials said Thursday, the latest in an array of scenarios following President Trump’s decision this month to remove all troops there. The options, presented by military officials, would represent a reversal from the American withdrawal Mr. Trump wanted. It also would modify U.S. objectives—from countering Islamic State extremists to also safeguarding oil fields…