Set the Instant Pot to 'Sauté' mode and heat the olive oil.
Add the onions, carrots, and celery, and sauté for 2-3 minutes until softened.
Stir in the garlic, salt, pepper, thyme, and oregano, and cook for another 30 seconds.
Pour in the chicken broth and water, then add the bay leaf and chicken.
Close the lid, set the valve to 'Sealing,' and cook on 'Manual' (High Pressure) for 10 minutes.
Allow a natural release for 10 minutes, then carefully release the remaining pressure.
Remove the chicken, shred it with two forks, and return it to the pot.
Add the egg noodles and set the Instant Pot to 'Sauté' mode. Cook for 5-6 minutes or until noodles are tender.
Stir in lemon juice (if using) and garnish with fresh parsley before serving.