Added a simple Testbed tool for repeatedly running templated Autogen scenarios with tightly-controlled initial conditions. (#455)

* Initial commit of the autogen testbed environment.

* Fixed some typos in the Testbed README.md

* Added some stricter termination logic to the two_agent scenario, and swiched the logo task from finding Autogen's logo, to finding Microsoft's (it's easier)

* Added documentation to testbed code in preparation for PR

* Added a variation of HumanEval to the Testbed. It is also a reasonable example of how to integrate other benchmarks.

* Removed ChatCompletion.start_logging and related features. Added an explicit TERMINATE output to HumanEval to save 1 turn in each conversation.

* Added metrics utils script for HumanEval

* Updated the requirements in the README.

* Added documentation for HumanEval csv schemas

* Standardized on how the OAI_CONFIG_LIST is handled.

* Removed dot-slash from 'includes' path for cross-platform compatibility

* Missed a file.

* Updated readme to include known-working versions.