feat: IBM Db2 - lazy connection + closing methods (#3664)

Co-authored-by: Sebastian Husch Lee <10526848+sjrl@users.noreply.github.com>

Author: anakin87

integrations/ibm_db/src/haystack_integrations/components/retrievers/ibm_db/embedding_retriever.py

@@ -76,6 +76,12 @@ def run(
         )
         return {"documents": docs}
 
+    def close(self) -> None:
+        """
+        Release the synchronous resources of the underlying Document Store.
+        """
+        self.document_store.close()
+
     def to_dict(self) -> dict[str, Any]:
         """
         Serializes the component to a dictionary.