Allow strict mode with @DgsRuntimeWiring

[sjohnr]

Pull Request type

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
• Other (please describe):

Changes in this PR

• Invoke checkTypeResolverExists() after @DgsRuntimeWiring to allow strict mode to be enabled with type resolvers registered via @DgsRuntimeWiring

Prior to this PR, enabling strict mode (dgs.graphql.strict-mode.enabled=true) could cause failures if applications use the RuntimeWiring.Builder to register type resolvers in methods annotated with @DgsRuntimeWiring. This PR moves the logic in DgsSchemaProvider to only automatically register type resolvers for interface and union types after callbacks to user code (@DgsScalar, @DgsDirective, @DgsData, @DgsTypeResolver, @DgsCodeRegistry, but mainly @DgsRuntimeWiring).

This allows applications to register custom type resolvers for interface and union types with strict mode enabled, as in the following example:

@DgsComponent
public class MyRuntimeWiring {
    @DgsRuntimeWiring
    public RuntimeWiring.Builder runtimeWiring(RuntimeWiring.Builder builder) {
        builder.type("MyInterfaceType", type -> type.typeResolver(new MyInterfaceTypeResolver()));
        builder.type("MyUnionType", type -> type.typeResolver(new MyUnionTypeResolver()));
        return builder;
    }
}

Closes gh-2180