refactor: move the embedding to the rag module and abstract the rerank runner for extension (#9423)

api/core/entities/embedding_type.py

@@ -0,0 +1,10 @@
+from enum import Enum
+
+
+class EmbeddingInputType(Enum):
+    """
+    Enum for embedding input type.
+    """
+
+    DOCUMENT = "document"
+    QUERY = "query"