The Trump administration's immigration policies are going to be a drag on the Massachusetts economy, which counts on thousands of new arrivals to the country each year just to maintain the labor force, a new report finds. Immigrants make up nearly a quarter of the state's work force and have an outsized role in higher education, universities, hospitals and the life sciences industry, according to a report by Boston Indicators, an arm of the Boston Foundation, and the MassINC Policy Center.