Audiences who visit the Ravinia Festival this weekend for an opening concert featuring the Chicago Symphony Orchestra, pop artist Lizzo and classical pianist Yunchan Lim will likely see and hear a few improvements. They’ll be the first to experience the results of a $70 million makeover. The Highland Park venue’s signature stage, called the Hunter Pavilion, is bigger, freshly designed and features a brand new orchestra shell with enhanced acoustics. The new shell is inspired by the stained-glass