[ticket/11441] Add _test prefix to user loader test filename.

PHPBB3-11441
[ticket/11441] Correct/fix class name of user loader test.

PHPBB3-11441
[ticket/11441] Update/correct copyright year of user loader test.

PHPBB3-11441
[ticket/11441] Use setUp() in phpbb_user_loader_test.

PHPBB3-11441
[ticket/11441] Split user loader tests into multiple test methods.

PHPBB3-11441
Merge remote-tracking branch 'bantu/ticket/11441' into develop

* bantu/ticket/11441:
  [ticket/11441] Split user loader tests into multiple test methods.
  [ticket/11441] Use setUp() in phpbb_user_loader_test.
  [ticket/11441] Update/correct copyright year of user loader test.
  [ticket/11441] Correct/fix class name of user loader test.
  [ticket/11441] Add _test prefix to user loader test filename.