Add HumanEval and HumanEval+

[lewtun]

The HumanEval and HumanEval+ benchmarks are stables for benchmarking code capabilities of base LLMs. It would be nice to include them in lighteval so one doesn't have to switch to another framework like BigCode's

References:

• HumanEval: https://github.com/openai/human-eval
• HumanEval+: https://arxiv.org/abs/2305.01210
• Implementation: https://github.com/evalplus/evalplus?tab=readme-ov-file
• BigCode eval harness: https://github.com/bigcode-project/bigcode-evaluation-harness/tree/main

[0-hero]

+1, would be nice to have