Feature: Parallel function-calling for AI Assistants

[cgillum]

Today, the AI assistant triggers can only be invoked one-at-a-time. However, for performance reasons, it can be useful to support parallel function calling, especially since interacting with OpenAI APIs for advanced models like GPT-4 can be time consuming.

This issue tracks adding support for parallel function-calling, which is already a feature of OpenAI's function calling API.