[v1.14] Add composite embedders and pooling for huggingface embedders (experimental)

[Strift]

This issue follows the changes related to Meilisearch v1.14.0 mega issue.

Description

Update embedders API to be compatible with Meilisearch v1.14.0

For more context, see the related issue in Meilisearch: meilisearch/meilisearch#5343

Tasks

• Add new pooling parameter for huggingFace embedders
• Add new composite source for embedders

For reference, here's how this works using Meilisearch JS SDK:

client
  .index('index_name')
  .updateEmbedders({
    embedder_name: {
      source: "composite",
      searchEmbedder: {
        source: "huggingFace",
        model:
          "sentence-transformers/paraphrase-multilingual-MiniLM-L12-v2",
        pooling: "useModel",
      },
      indexingEmbedder: {
        source: "huggingFace",
        model:
          "sentence-transformers/paraphrase-multilingual-MiniLM-L12-v2",
        documentTemplate: "{{doc.title}}",
        pooling: "useModel",
        documentTemplateMaxBytes: 500,
      },
    },
  });