`ElasticsearchSparseEmbeddingRetriever` (precomputed sparse)

[davidsbatista]

• Add a new retrieval method (e.g. _sparse_vector_retrieval) analogous to _embedding_retrieval and _bm25_retrieval, which builds and executes a sparse_vector query using a precomputed query_vector.
• New retriever component: input query_sparse_embedding (e.g. from Fastembed); calls the document store’s sparse retrieval method.
• ES: sparse_vector query (precomputed query_vector).