REFACTOR: Tidy-up embedding endpoints config.

[romanrizzi]

Two changes worth mentioning:

1. .instance returns a fully configured embedding endpoint ready to use.
2. All endpoints respond to the same method and have the same signature - perform!(text). It's no longer a class method.

This makes it easier to reuse them when generating embeddings in bulk.

[xfalcox]

Why the divide between HuggingFaceText and TeiEmbeddings ? They are the same service, this separation makes it hella confusing.

Also TeiEmbeddings is another case of "Text Embeddings Inference Embeddings"

[romanrizzi]

Why the divide between HuggingFaceText and TeiEmbeddings ? They are the same service, this separation makes it hella confusing.

Also TeiEmbeddings is another case of "Text Embeddings Inference Embeddings"

Fair enough. I'll merge it back but leave rerank and classify as class methods.