Switch to using pydantic_settings for command line and environment variable management

[JonahSussman]

Switch to using https://docs.pydantic.dev/latest/concepts/pydantic_settings/ for command line parsing and using environment variables. This will make creating an application together from a config much easier so we don't have random environment variable checks everywhere.

[shawn-hurley]

@JonahSussman is this covered in your config PR?