Phi-2

[matheper]

This PR contains a set of small improvements and adaptations made for experiments using Phi-2 model. Most of this code was previously reviewed and merged into the phi2 branch. Now it is being merged into the main branch.

• Loading model configs from yaml
• Fix a hard-coded tokenization cleaning in dln.score
• Mini-batch calls to VLLM models
• Check and fail early if a request is larger than the model's maximum sequence length
• v3.6 backward template
• Add top-k to read_results
• Add new scripts
• Document the DLN components in the main README
• Document and type hinting dln.datasets

TODO in a separate PR:

• Organize scripts in a better way / separate folders
• Document OpenAI change not allowing to request echo and logprobs at the same time

[matheper]

Thanks for re-reviewing everything @MarcCote!