SPRINGFIELD — With some understatement, U.S. District Judge Joan H. Lefkow summarized the task for the state official who manages Illinois’ checkbook: “unenviable.”It was that way before this week, as limited revenue and an ongoing budget dispute have forced the comptroller to prioritize certain payments over others. That’s led to credit downgrades, multiple lawsuits and a bill backlog that’s ballooned to around $14 billion.But the situation became more unenviable after Lefkow ordered …