5355: Support fetching the pooling method from the model configuration r=Kerollmops a=dureuill
# Pull Request
## Related issue
Fixes#5354
## What does this PR do?
- Fetches the pooling configuration from the model repository
- Use a pooling method that depends on the pooling configuration of that model.
- Allow overriding the pooling method with a new huggingFace embedder parameter `pooling`
- for backward-compatibility with Meilisearch v1.13
- for compatibility with embedders that exhibit the same behavior as Meilisearch v1.13
- Handle the default value of that new parameter
- for compatibility, when importing a db/a dump, it should be set to `forceMean`
- when (re)set from the settings for an embedder, it should be set to `useModel`
Co-authored-by: Louis Dureuil <louis@meilisearch.com>
