Add sync support for the AsyncPostgresStore (#2673)

libs/langgraph/tests/test_pregel_async.py

@@ -12621,9 +12621,19 @@ async def test_store_injected_async(checkpointer_name: str, store_name: str) ->
             )
             return {"count": 1}
 
+    def other_node(inputs: State, config: RunnableConfig, store: BaseStore):
+        assert isinstance(store, BaseStore)
+        store.put(("not", "interesting"), "key", {"val": "val"})
+        item = store.get(("not", "interesting"), "key")
+        assert item is not None
+        assert item.value == {"val": "val"}
+        return {"count": 0}
+
     builder = StateGraph(State)
     builder.add_node("node", Node())
+    builder.add_node("other_node", other_node)
     builder.add_edge("__start__", "node")
+    builder.add_edge("node", "other_node")
 
     N = 500
     M = 1