Add the chicken, fire-roasted tomatoes, carrots, potatoes, chicken broth, buffalo sauce, onion powder, garlic powder and salt to the Instant Pot. Set the cream cheese on the counter to soften while the soup is cooking. Cover and secure the lid. Make sure valve is set to sealing. Press the manual pressure cook button (low pressure) and set the timer to 5 minutes. Once the timer beeps indicating the time is up, move valve to venting for quick release. Turn the Instant Pot to the lowest setting on the saute function. Add in the cream cheese and stir until it melted. In a small bowl stir together 1 tablespoon of cornstarch with 2 tablespoons of water. Stir the cornstarch slurry into the pot. The chili will thicken in just a few minutes. Ladle the chili into bowls and top with bleu cheese crumbles and extra celery, if desired