Add the chicken, celery, carrots, onion, garlic cloves, thyme, and rosemary into the slow cooker. Pour in the chicken stock. Cook on high for 3-4 hours or low for 6-8 hours. During the last 15 minutes, remove the chicken breast. Shred with a fork. Add the chicken breast back in, as well as the egg noodles. Cook for the last 15 minutes.