A proposal to allow bow-hunting for deer on town-owned conservation land is stirring debate in Weston, where residents question whether using archers to cull the town’s fast-growing deer population is practical and necessary, or cruel and dangerous. If the Board of Selectmen votes to allow the plan, which is being proposed by the town’s Conservation Commission, Weston will join a growing number of suburban communities looking to hunters to help limit the burgeoning population of deer in the eastern part of the state.