OpenAIEmbeddings to core module

[javipacheco]

This PR removes OpenAIEmbeddings and I'm adding the implementation of this to com.xebia.functional.xef.llm.Embeddings and now com.xebia.functional.xef.embeddings.Embeddings is not necessary

[Intex32]

Considering the scope of the issue, LGTM.
Possible renames for EmbeddingsProvider I can think of are EmbeddingsStrategy and EmbeddingsService.

For another issue, I suggest making the embedQuery function an extension function that calls embedDocuments, as it is just a special case of the latter until now.
Additionally, the chunkSize should be passed in the constructor of EmbeddingsProvider and not be part of the Embeddings interface function signature, as the chunk size is specific to this implementation.

These are just my humble thoughts.

[raulraja]

Looks great @javipacheco , thanks!

In this or another PR, we must address the number and size of messages for embedding requests. We have been defaulting to 400 or configured chunk size, but we know the max content length of the model, which would allow us to send fewer and lengthier requests.

[Montagon]

🚀