UserPermissionsForm should not use overridden permissions

Problem/Motivation

When using a ConfigFactoryOverrideInterface to override permissions, these new permissions will be displayed on /admin/people/permissions. So when saving the form, the overridden permissions will be saved to the database.

Steps to reproduce

Implement a permission override in a module:

namespace Drupal\foo\Config;

use Drupal\Core\Cache\CacheableMetadata;
use Drupal\Core\Config\ConfigFactoryOverrideInterface;
use Drupal\Core\Config\StorageInterface;

/**
 * Example configuration override.
 */
class PermissionOverrides implements ConfigFactoryOverrideInterface {

  /**
   * {@inheritdoc}
   */
  public function loadOverrides($names) {
    $overrides = [];
    if (in_array('user.role.webmestre', $names)) {
      $overrides['user.role.webmestre']['permissions'][9999] = 'foo';
    }
    return $overrides;
  }

  /**
   * @return string
   */
  public function getCacheSuffix() {
    return 'foo';
  }

  /**
   * @param string $name
   *
   * @return \Drupal\Core\Cache\CacheableMetadata
   */
  public function getCacheableMetadata($name) {
    return new CacheableMetadata();
  }

  /**
   * @param mixed $name
   * @param string $collection
   *
   * @return \Drupal\Core\Config\StorableConfigBase|null
   */
  public function createConfigObject($name, $collection = StorageInterface::DEFAULT_COLLECTION) {
    return NULL;
  }

}

Then browse to /admin/people/permissions and save the form.
The overridden permission is saved in the config.

Proposed resolution

UserPermissionsForm should load the permissions from the config without any override.

Remaining tasks

N/A

User interface changes

N/A

Introduced terminology

N/A

API changes

N/A

Data model changes

N/A

Release notes snippet

N/A