DHAKA, Bangladesh — They had seen the images of Rohingya Muslim refugees arriving hungry and exhausted after traveling days without food to reach Myanmar’s border with Bangladesh. They had heard the stories of gunshot wounds and midnight escapes from angry mobs and soldiers. So when the rickshaw pullers, tea stall vendors and other villagers in northern Bangladesh’s Mymensingh district were asked to give, they did — in days raising $10,000 to donate to hospitals and refugee camps helping those who fled in what is now Asia’s largest refugee crisis in decades.