The Embers, Mr. Kelly’s, the London House, Toulouse and the Blue Note are just a few of the many watering holes that used to dot Rush Street and Chicago’s Loop, offering top-notch live entertainment.Thoughts of these once-popular, long-gone venues flooded my memories when I recently attended “I Left My Heart,” the current production at the Mercury Theater, 3745 N. Southport Ave., whose Executive Producer L. Walter Stearns bills as “A salute to the music of Tony Bennett.” And what a …