drupal_render() and drupal_render_root() replaced with Renderer service

The drupal_render() and drupal_render_root() functions are deprecated and have been replaced with methods on the Renderer service.

Before:

drupal_render($elements, $is_recursive_call);
drupal_render_root($elements);

After:

 \Drupal::service('renderer')->render($elements, $is_recursive_call);
 \Drupal::service('renderer')->renderRoot($elements);