Make sure py__get__ is defined on all values

Also define matches_signature on all signatures, there's definitely cases where that might be called

jedi/plugins/stdlib.py

@@ -335,7 +335,7 @@ def builtins_isinstance(objects, types, arguments, inference_state):
 
 
 class StaticMethodObject(ValueWrapper):
-    def py__get__(self, instance, klass):
+    def py__get__(self, instance, class_value):
         return ValueSet([self._wrapped_value])