[V2] Remove the DI_Container and Hook_Loader from Middleware

[gin0115]

Registration Middleware currently has the following defined on the Interface

/**
 * Set the hook loader.
 *
 * @param Hook_Loader $hook_loader
 */
public function set_hook_loader( Hook_Loader $hook_loader ): void;

/**
 * Set the DI Container
 *
 * @param DI_Container $container
 */
public function set_di_container( DI_Container $container ): void;

These should be removed as just using the _container_aware_traits and matching interfaces should be enough to populate these.