[feature/auth-refactor] Refactor auth in acp_board

Changes the acp_board code to directly call the auth providers out
of the $auth_providers variable that is populated by the
phpbb_container.

PHPBB3-9734
[feature/auth-refactor] Fix indentation on acp_board

PHPBB3-9734
[feature/auth-refactor] Fix errors in acp_board

Fixes errors introduced by the last several commits.

PHPBB3-9734