MDL-45242 Lib: Replace calls to deprecated functions

In all cases changes have been kept to a minimum while not making
the code completely horrible. For example, there are many instances
where it would probably be better to rewrite a query entirely, but
I have not done that (in order to reduce the risk of changes).

lib/authlib.php

@@ -1102,7 +1102,7 @@ function signup_setup_new_user($user) {
     $user->secret      = random_string(15);
     $user->auth        = $CFG->registerauth;
     // Initialize alternate name fields to empty strings.
-    $namefields = array_diff(get_all_user_name_fields(), useredit_get_required_name_fields());
+    $namefields = array_diff(\core\user_fields::get_name_fields(), useredit_get_required_name_fields());
     foreach ($namefields as $namefield) {
         $user->$namefield = '';
     }