We open source Metis in Amphion

[HeCheng0625]

✨ Description

We introduce Metis, a foundation model for unified speech generation. We open source inference codes, model checkpoints of the pre-trained and fine-tuned models.

👨‍💻 Changes Proposed

• Add metis code
• Add huggingface models
• Change README.md

🧑‍🤝‍🧑 Who Can Review?

@RMSnow @jiaqili3

✅ Checklist

• Code has been reviewed
• Code complies with the project's code standards and best practices
• Code has passed all tests
• Code does not affect the normal use of existing features
• Code has been commented properly
• Documentation has been updated (if applicable)
• Demo/checkpoint has been attached (if applicable)

[yuantuo666]

Some typo needs to be corrected.

[yuantuo666]

LGTM

[rikabi89]

What is diff between Metis-Base and Metis-TTS. Is Metis-TTS basically exact same as MaskGCT?