Improvement for item_spawner_device

Item_spawner_device is similar to item_granter_device in essence, however item_granter is a newer device and has great features that need to be moved to item_spawner_device.

The problem is that toggling in item_spawner_device works extremely awkward and requires me to toggle 7 times if I want to spawn a seventh item. If I add the same functions to it as item_granter:

        # Sets the next item to be granted.
        #  * `Index` should be between `0` and the available item count - 1.
        #  * Calling `SetNextItem` with an invalid index will do nothing.
        SetNextItem<public>(Index:int):void = external {}

Then it would be a great opportunity to optimize memory costs and usability.

@2GHSamburskoy Thank you for your feedback. While I cannot guarantee a response, I can confirm that this has been forwarded to the appropriate team.