Compatibility with WPGraphQL v0.4.0

[jasonbahl]

WPGraphQL v0.4.0 (upcoming) introduces some breaking changes to the TypeRegistry.

WPGraphQL for ACF will need some updates to play nice with the core WPGraphQL update.

The update to WPGraphQL v0.4.0 enables the GraphQL Schema to be cleared properly, enabling better integration tests with Codeception, which will severely increase the code quality of the core plugin and extensions such as ACF.

---

The changes needed for this extension to play nice are pretty minor:

• Hook the main Config to init_graphql_type_registry instead of graphql_register_types
• Have the Config class accept TypeRegistry as an argument, and set it in the class as a class var
• Replace instances of TypeRegistry:: static method calls with $this->type_registry (using the ^ instance passed into the class)
• Replace the resolveType methods to use the type_registry passed to the class instead of static Types:: methods
• Refactor tests to be more granular (the result and primary goal of the new WPGraphQL::__clear_schema() ability). . .now tests can be MUCH more granular, readable, and maintainable, instead of registering everything all up front, individual tests can register exactly what they need!