GH-1826 Fix EmbeddingModel's usage on Document#embedding

- Since the Document object's reference to the `embedding` is deprecated and will be removed, the VectorStore implementations require a way to store the embedding of the corresponding Document objects

     - One way to fix this is, to have the EmbeddingModel#embed to return the embeddings in the same order as that of the Documents passed to it.

       - Since both the Document and embedding collections use the List object, their iteration operation will make sure to keep them in line with the same order.

       - A fix is required to preserve the order when batching strategy is applied.
	  - Updated the Javadoc for BatchingStrategy
          - Fixed the Document List order in TokenCountBatchingStrategy

    - Refactored the vector store implementations to update this change

Resolves #GH-1826

vector-stores/spring-ai-pinecone-store/src/main/java/org/springframework/ai/vectorstore/PineconeVectorStore.java

@@ -124,11 +124,12 @@ public class PineconeVectorStore extends AbstractObservationVectorStore {
 	 * @param namespace The namespace to add the documents to
 	 */
 	public void add(List<Document> documents, String namespace) {
-		this.embeddingModel.embed(documents, EmbeddingOptionsBuilder.builder().build(), this.batchingStrategy);
+		List<float[]> embeddings = this.embeddingModel.embed(documents, EmbeddingOptionsBuilder.builder().build(),
+				this.batchingStrategy);
 		List<Vector> upsertVectors = documents.stream()
 			.map(document -> Vector.newBuilder()
 				.setId(document.getId())
-				.addAllValues(EmbeddingUtils.toList(document.getEmbedding()))
+				.addAllValues(EmbeddingUtils.toList(embeddings.get(documents.indexOf(document))))
 				.setMetadata(metadataToStruct(document))
 				.build())
 			.toList();