By Dan Williams JERUSALEM (Reuters) -The United States upgraded its diplomatic mission to the Palestinians on Thursday, reversing a Trump administration move ahead of a planned visit by President Joe Biden. The “Palestinian Affairs Unit” (PAU) was renamed the “U.S. Office of Palestinian Affairs” (OPA) and will report directly to Washington “on substantive matters”. Prior to becoming the PAU, it had been the U.S. consulate in Jerusalem and a focus of Palestinian statehood goals in the city. Former President Donald Trump formally closed the consulate and redesignated it as the PAU within the U.S…