Transition of application credit creation to the Partner API

As of Admin API version 2023-07, we are deprecating creating application credits through the Admin API. Both the REST resource, and the GraphQL mutation will have their ability to create application credits deprecated. Going forward, create application credits using our new appCreditCreate mutation in the Partner API.

This change will allow us to implement new features for application credit creation, such as allowing Partners to issue credits to Shops that have uninstalled their app.