Integrate MBPP benchmarks

[azrv]

Solves #914

Run with python3 gpt_engineer/benchmark gpt_engineer/core/default/simple_agent.py mbpp

Here are my results running for the first 47 tasks using gpt-4-0125-preview model

--- Results ---
Total time: 465.19s
Completely correct tasks: 40/47
Total correct assertions: 123/142
Average success rate: 86.52482269503545% on 47 tasks
--- Results ---

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 84.33%. Comparing base (67e8a3f) to head (2649d8f).
Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1103      +/-   ##
==========================================
+ Coverage   84.29%   84.33%   +0.04%     
==========================================
  Files          27       27              
  Lines        1566     1564       -2     
==========================================
- Hits         1320     1319       -1     
+ Misses        246      245       -1     

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[captivus]

As discussed, please check for OpenAI API key in the .env file. Thanks!