Agent Protocol Support

[pbharrin]

This PR adds support for the Agent Protocol. #683 There is a file called api.py which implements the protocol and scripts/test_api.py which shows how it can be used.

Most options are supported except improve code mode. It is not impossible to support this mode, it will just take some additional code and documentation.

[ATheorell]

Agent Protocol Support
The test script runs very smoothly.
I spent quite a long time, trying to get gpt-engineer to communicate with https://github.com/Significant-Gravitas/Auto-GPT/tree/master/benchmark via the protocol, while running locally. Took a long time to get their code to run at all and tried many commits. Commit Fix API Mode #5209 (only 5 hours old) of AutoGPT runs and sends requests to gpt-engineer, but currently, only errors come out.
I merged now, so that people can already start using it, but once the AutoGPT development stabilizes, we should probably debug why all tests fail currently.

[AntonOsika]

🚀