Draft: Add Experimental Duo Chat Endpoint

Implements Testing DuoChat on GPT (#591 - closed)

This is an alternative implementation to Add duo chat test with response validation and ... (!574 - merged) which attempts to avoid the necessity to use web sockets. While it does indeed appear to be feasible to use xk6-websockets to listen for a response, it adds a new layer of complexity to the entire setup as it requires compiling a custom binary with the extension enabled.

Instead, we can consider making use AiMessages which will allow use to use standard HTTP Post requests using the GraphQL api. Upon observing this API we can see that a payload of 1 will be returned after submitting the question (including details of the query), and upon generating a response we then get a second node including the details generated by DUO chat in response.