Arlington Heights is moving forward on a proposal to let people “sip and stroll” through the village’s downtown. Trustees voted in favor of a new “social district” pilot program on Monday night. The program would let participating bars and restaurants sell drinks to go. Patrons could consume their cocktails, as long as they remain within a four-block area known as the “alfresco zone.” The pedestrian-only area has remained a busy warm-weather des…