Boston Mayor Marty Walsh, a Democrat, was confirmed Monday by the Senate to be the secretary of labor, set to take the reins of an agency that is central to President Joe Biden’s worker-friendly agenda. He rose to prominence in Boston through the building trades unions after dropping out of college to work in construction. He also served in the Massachusetts House of Representatives. Walsh, 53, has supported labor policies including the PRO Act, a proposal to update labor laws and give workers more ability to organize at work that the House passed last year. He also has supported efforts to raise the minimum wage. Walsh will lead a Labor Department navigating a complicated economic and public health crisis, with an estimated 18 million people collecting unemployment benefits and others who have left the workforce since last year.