Views plugins may now react to removal of dependencies

In order to prevent the deletion of the whole View when a dependency is removed, Views plugins can now react to dependency removal by implementing Drupal\views\Plugin\DependentWithRemovalPluginInterface and implementing the onDependencyRemoval method.

Example from \Drupal\views\Plugin\views\field\EntityField:

  /**
   * {@inheritdoc}
   */
  public function onDependencyRemoval(array $dependencies) {
    // See if this handler is responsible for any of the dependencies being
    // removed. If this is the case, indicate that this handler needs to be
    // removed from the View.
    $remove = FALSE;
    // Get all the current dependencies for this handler.
    $current_dependencies = $this->calculateDependencies();
    foreach ($current_dependencies as $group => $dependency_list) {
      // Check if any of the handler dependencies match the dependencies being
      // removed.
      foreach ($dependency_list as $config_key) {
        if (isset($dependencies[$group]) && array_key_exists($config_key, $dependencies[$group])) {
          // This handlers dependency matches a dependency being removed,
          // indicate that this handler needs to be removed.
          $remove = TRUE;
          break 2;
        }
      }
    }
    return $remove;
  }