SPRINGFIELD — After serving 10 years as leader of the Illinois Senate, President John J. Cullerton announced his retirement from the state General Assembly Thursday evening.“I came to the job with great optimism and enthusiasm, ready to tackle the challenges confronting Illinois, and with great expectations for moving forward to solve some of the crises our state faced,” Cullerton said in a statement.He said his retirement is effective in January but a specific date hasn’t been set.“During a …