Russell T. Vought, President Trump's nominee to run the Office of Management and Budget, told Senate lawmakers in a confirmation hearing on Wednesday that he supported work requirements for low-income Americans receiving publicly subsidized health insurance, a policy that Mr. Trump pursued in his first term but that the Biden administration mostly reversed. The comments suggested that the Trump administration was likely to seek a broad overhaul of how the federal government administers Medicaid, the joint federal-state health insurance program for more than 70 million people.