[ticket/12224] Add template wrapper method to assign block arrays

Add one more wrapper template method for the function assign_block_vars() which
takes a 2-dimensional array as a parameter
and calls assign_block_vars() in a loop to assign the whole block loop at once.
This can make the core a little bit more expendable from the point of
developing extensions as it allows to pass the data to events before
it's being assigned to template.

PHPBB3-12224
[ticket/12251] Sort IM profile fields alphabetically

PHPBB3-12251
[ticket/12251] Deactivate outdated profile fields by default

PHPBB3-12251
[ticket/12251] Enable displaying profile fields on memberlist, posts and pms

PHPBB3-12251
[ticket/12251] Load profile fields by default on posts, pms and memberlist

PHPBB3-12251
[ticket/12251] Add string validation for a-zA-Z0-9 and underscore

PHPBB3-12251
[ticket/12251] Remove leading whitespace on doc blocks

PHPBB3-12251
[ticket/12256] Selecting founders is fetching $sql instead of $result

PHPBB3-12256
Merge pull request #2099 from bantu/ticket/12256

[ticket/12256] Selecting founders is fetching $sql instead of $result
Merge pull request #2089 from nickvergessen/ticket/12251

[ticket/12251] Clean up and Enhancement of Custom Profile Fields
[ticket/12224] Add assign_block_vars_array() test.

Add tests, also change return value to null.

PHPBB3-12224
Merge remote-tracking branch 'rxu3/ticket/12224' into develop

* rxu3/ticket/12224:
  [ticket/12224] Add assign_block_vars_array() test.
  [ticket/12224] Add template wrapper method to assign block arrays