feat (RAG): Implement configurable search mode in RAGQueryConfig

Signed-off-by: Varsha Prasad Narsing <varshaprasad96@gmail.com>

llama_stack/providers/inline/vector_io/faiss/faiss.py

@@ -99,9 +99,15 @@ class FaissIndex(EmbeddingIndex):
         # Save updated index
         await self._save_index()
 
-    async def query(self, embedding: NDArray, k: int, score_threshold: float) -> QueryChunksResponse:
+    async def query(
+        self,
+        embedding: NDArray,
+        query_string: Optional[str],
+        k: int,
+        score_threshold: float,
+        mode: Optional[str],
+    ) -> QueryChunksResponse:
         distances, indices = await asyncio.to_thread(self.index.search, embedding.reshape(1, -1).astype(np.float32), k)
-
         chunks = []
         scores = []
         for d, i in zip(distances[0], indices[0], strict=False):