Update OpenAI settings to support new model versions and increased token counts.

OpenAI is updating its models, pricing, and context length (as well as other feature enhancements). Older models now face deprecation as well.

See https://openai.com/blog/function-calling-and-other-api-updates for details to implement.

Note, this has a deadline of September 13th, 2023, before model currently pointed to by Sock is discontinued.