SPRINGFIELD — Separated powers overlapped Tuesday when legislators and the governor observed Illinois’ top court in action during a rare evening session. Gov. Bruce Rauner and General Assembly members filled the Illinois Supreme Court chamber to witness oral arguments regarding the constitutionality of a statute that was amended by some of the very people who sat in the room. Supreme Court spokesman Joseph R. Tybor said the high court last held evening arguments sometime in the late 1800s. That unusual …