New pipeline to create the code-generation dataset.

What does this merge request do and why?

Reference: #133

This MR introduce a new pipeline to generate a code-generation dataset. This code-generation dataset uses gitlab codebases to reflect real-world code-generation complexity.

The process of generating this dataset:

1. Chunk gitlab code bases into blocks of functions and classes.
2. Let an LLM to read the code and ask it to generate the prompt that would generate the code.

How to set up and validate locally

poetry run promptlib duo-chat make-dataset-code-generation --config-file data/config/duochat_make_dataset_code_generation.json --test-run

Merge request checklist

• I've ran the affected pipeline(s) to validate that nothing is broken. https://console.cloud.google.com/bigquery?authuser=0&project=dev-ai-research-0e2f8974&ws=!1m5!1m4!4m3!1sdev-ai-research-0e2f8974!2sduo_chat_experiments!3shyang_code_generation_dataset_delme
• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.