Deprecate user_role_permissions()

There no need to postpone this.

1. +++ b/core/modules/user/user.module
   @@ -255,9 +255,10 @@ function user_role_permissions(array $roles) {
    function _user_role_permissions_update($roles) {
   +  $entities = Role::loadMultiple($roles);
      $role_permissions = [];
      foreach ($roles as $rid) {
   -    $role_permissions[$rid] = \Drupal::config("user.role.$rid")->get('permissions') ?: [];
   +    $role_permissions[$rid] = $entities[$rid]->getPermissions() ?: [];
      }
      return $role_permissions;
    }
   

   This function shouldn't be changing at all. It will be reomved in Drupal 11.

2. +++ b/core/tests/Drupal/Tests/Core/Session/PermissionsHashGeneratorTest.php
   @@ -252,9 +253,10 @@ public function testGenerateNoCache() {
    if (!function_exists('user_role_permissions')) {
    
      function user_role_permissions(array $roles) {
   +    $entities = Role::loadMultiple($roles);
        $role_permissions = [];
        foreach ($roles as $rid) {
   -      $role_permissions[$rid] = [];
   +        $role_permissions[$rid] = $entities[$rid]->getPermissions() ?: [];
        }
        return $role_permissions;
      }
   

   This code should be removed because we change the PermissionsHashGenerator

Here's the deprecations and the uses in core replaced. Now we need to add test coverage of the deprecated methods. To test the deprecation and to ensure we don't break them until they are removed.

No interdiff because of #4.

We need to complete the issue summary and change record.