Sara Bareilles has a talent for finding the human center of things. She is currently starring in the revival of Stephen Sondheim’s “Into the Woods.” In the musical, she plays the Baker’s Wife, a part that Joanna Gleason—who played the wife when the show débuted on Broadway, in 1987—first made famous, and that Imelda Staunton and Amy Adams later performed. It’s a role that’s passed like a crown from one talented actress to the next.