[feature/passwords] Use dependency injection for helper

This will now be used instead of manually loading the passwords helper
instance in the passwords manager.

PHPBB3-11610

phpBB/config/passwords.yml

@@ -50,4 +50,8 @@ services:
         arguments:
             - @config
             - @passwords.driver_collection
+            - @passwords.helper
             - %passwords.algorithm%
+
+    passwords.helper:
+        class: phpbb_passwords_helper