[ticket/9388] Add support for making <select> options able to toggle settings.

PHPBB3-9388
[ticket/9388] Display only the settings for the auth method that's selected.

PHPBB3-9388
[ticket/9388] Display only the settings for the selected search backend.

PHPBB3-9388
[ticket/9388] Use the new toggle function for the avatar type <select>.

PHPBB3-9388
[ticket/9388] Fix unit tests.

PHPBB3-9388
[ticket/9388] Reopen <fieldset> after auth templates.

PHPBB3-9388
[ticket/9388] Do not nest the <fieldset> tags in the OAuth settings.

PHPBB3-9388
[ticket/9388] Use "togglable" instead of "toggable"

PHPBB3-9388
Merge pull request #2420 from prototech/ticket/9388

[ticket/9388] Only display the settings for the selected method in the auth and search ACP pages.

* prototech/ticket/9388:
  [ticket/9388] Use "togglable" instead of "toggable"
  [ticket/9388] Do not nest the <fieldset> tags in the OAuth settings.
  [ticket/9388] Reopen <fieldset> after auth templates.
  [ticket/9388] Fix unit tests.
  [ticket/9388] Use the new toggle function for the avatar type <select>.
  [ticket/9388] Display only the settings for the selected search backend.
  [ticket/9388] Display only the settings for the auth method that's selected.
  [ticket/9388] Add support for making <select> options able to toggle settings.