Add test designer and test executor agents

[MaxAnfilofyev]

https://arxiv.org/pdf/2312.13010.pdf

The process begins by inputting tasks/code generation requirements/descriptions into the code generation agent (Agent#1: the programmer agent). Subsequently, the test case generator (Agent#2: the test designer agent) is tasked with generating test cases, which are used to evaluate the correctness of the code snippets produced by the programmer agent. The code snippets and test cases are collected by the test executor agent (Agent#3) and executed in the local environment (local terminal) to obtain feedback (i.e., whether the code passes all tests and the error message if the code fails for some tests). If the test executor agent finds that the code snippets pass all test cases, it will return the code to the user and finish the iteration. Otherwise, the test executor agent will return the test execution error messages to the programmer agent. The iteration then continues, with the programmer agent regenerating code snippets to address the issues identified in the feedback, and the test executor agent re-executes the new code and provides new feedback to the programmer agent, until the test executor agent finds that the code passes all the tests.