[ticket/13248] Use auth provider collection for getting provider

PHPBB3-13248
[ticket/13248] Allow specifying different auth provider in provider collection

PHPBB3-13248
[ticket/13248] Always use provider collection for getting provider

PHPBB3-13248
[ticket/13248] Correctly pass provider name

PHPBB3-13248
[ticket/13248] Use functional framework login method in tests

PHPBB3-13248
Merge pull request #3104 from marc1706/ticket/13248-alt

[ticket/13248] Login functions need to use provider collection for retrieving provider