Georgetown University should apologize for the ways it participated in slavery and benefited from the sale of Jesuit-owned slaves in the early 19th century, a university panel concluded in a report released Thursday that cast a stark spotlight on a troubling period of history at one of the nation’s top Catholic schools. The panel also urged the university to consider giving admission preference and financial aid to the descendants of slaves the Maryland Jesuits owned, including a large group sold in 1838 in part to pay off debts at the school the order ran in the District of Columbia.