Input fixes (#2541)

* Example use old SpriteList.on_update
* _generate_next_value_ is a staticmethod

Author: einarf

arcade/future/input/input_manager_example.py

@@ -213,7 +213,7 @@ def on_key_press(self, key, modifiers):
                 player.input_manager.allow_keyboard = False
 
     def on_update(self, delta_time: float):
-        self.player_list.on_update(delta_time)
+        self.player_list.update(delta_time)
         for label, player in zip(self.player_device_labels, self.players):
             position_x, position_y = player.position
             position_y += FLOAT_HEIGHT

arcade/future/input/inputs.py

@@ -37,6 +37,7 @@ def __new__(cls, value, *args, **kwargs):
     def __str__(self):
         return str(self.value)
 
+    @staticmethod
     def _generate_next_value_(name, *_):
         return name