[ticket/11862] Correct var names in user_delete() events due to prune-users

The prune-users feature modified the names of the used variables in this
function. However, the variable names for the two events in this function
were not changed to reflect that. This patch will take care of it.

PHPBB3-11862
[ticket/11691] Stagger the convertion of soft delete updates

PHPBB3-11691
[ticket/11691] Stagger user notification reconversion even more

PHPBB3-11691
[ticket/11691] Change detection of effectively_installed()

When start is set for a migration, it is not yet effectively installed.
So we just continue doing it...

PHPBB3-11691
[ticket/11691] Fix some more problems with softdelete update

* wrong order of arguments on sql_query_limit
* avoid "BIGINT UNSIGNED value is out of range" errors
* increase limit for the loop

PHPBB3-11691
[ticket/11691] Fix some minor comments

PHPBB3-11691
[ticket/11691] Add order by to the query

PHPBB3-11691
[ticket/11691] Fix typo in comment

PHPBB3-11691
[ticket/11691] Move purge code into new function

PHPBB3-11691
[ticket/11691] Fix table names and arguments/docs

PHPBB3-11691
[ticket/11852] Split filesystem and path_helper into 2 classes

PHPBB3-11852
[ticket/11852] Move tests to folder with new class name

PHPBB3-11852
[ticket/11852] Add class file

PHPBB3-11852
Merge remote-tracking branch 'Marc/ticket/11862' into develop

* Marc/ticket/11862:
  [ticket/11862] Correct var names in user_delete() events due to prune-users
[ticket/11862] Correct var names in user_delete() events due to prune-users

Fix comments after incorrect merge of previous PR.

PHPBB3-11862
Merge remote-tracking branch 'Marc/ticket/11862' into develop

* Marc/ticket/11862:
  [ticket/11862] Correct var names in user_delete() events due to prune-users
[ticket/11873] Do not hash very large passwords in order to safe resources.

PHPBB3-11873
[ticket/11873] Add unit test for large password input.

The password should be rejected quite fast.

PHPBB3-11873
Merge branch 'ticket/11873' into prep-release-3.0.12

* ticket/11873:
  [ticket/11873] Add unit test for large password input.
  [ticket/11873] Do not hash very large passwords in order to safe resources.
[prep-release-3.0.12] Update changelog for 3.0.12 release.