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-qdrant-store/src/main/java/org/springframework/ai/vectorstore/qdrant/QdrantVectorStore.java

@@ -127,12 +127,13 @@ public class QdrantVectorStore extends AbstractObservationVectorStore implements
 		try {
 
 			// Compute and assign an embedding to the document.
-			this.embeddingModel.embed(documents, EmbeddingOptionsBuilder.builder().build(), this.batchingStrategy);
+			List<float[]> embeddings = this.embeddingModel.embed(documents, EmbeddingOptionsBuilder.builder().build(),
+					this.batchingStrategy);
 
 			List<PointStruct> points = documents.stream()
 				.map(document -> PointStruct.newBuilder()
 					.setId(io.qdrant.client.PointIdFactory.id(UUID.fromString(document.getId())))
-					.setVectors(io.qdrant.client.VectorsFactory.vectors(document.getEmbedding()))
+					.setVectors(io.qdrant.client.VectorsFactory.vectors(embeddings.get(documents.indexOf(document))))
 					.putAllPayload(toPayload(document))
 					.build())
 				.toList();