SPRINGFIELD — A man became an informant thinking his help would allow police to throw out the drug charges against him.But he was still indicted a year after his arrest with police arguing he didn’t fully cooperate in the bargain.Now the state’s top court is set to rule on whether the charges should be dropped because of a due process violation.The Illinois Supreme Court is slated to decide this week whether the man, Anthony M. Stapinski, should go free or face a full trial for possession and delivery of …