Optimize PatchDiff with parallel processing

Add rayon dependency to Cargo.toml

Remove redundant patch tests

Update Cargo.lock with new dependencies

Remove profiling tests

feat: Add Finetune functionality and related files

- Introduce finetune.rs to manage fine-tuning workflows with OpenAI.
- Create finetune.md for documenting the finetuning process.
- Update Cargo.toml and Cargo.lock with necessary dependencies for finetuning.
- Add stats.json to track various parameters in the finetuning process.
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delete: remove stats.json file

Based only on the changes visible in the diff, this commit deletes the stats.json file.
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