Stop using deprecated web3.py interface (#1759)

* Refactor contract function call to support web3.py v5.0.0. (backwards compatible with v4)

python-packages/order_utils/stubs/web3/utils/datatypes.pyi

@@ -1,3 +1,12 @@
-class Contract:
-    def call(self): ...
+from typing import Callable
+
+
+class ContractFunctions:
+    def __getattr__(self, function_name) -> Callable:
+        ...
+    ...
+
+
+class Contract:
+    functions: ContractFunctions
     ...