Fix EZP-23595: delete row from ezuser_setting on deleteUser()

https://jira.ez.no/browse/EZP-23595

`UserService::createUser()` creates rows on `ezuser_setting` table, but `deleteUser()` does not.
This can lead to DB `Integrity constraint violation` errors.

Fix by removing the corresponding row from `ezuser_setting` table.

TODO:
 - [x] Add/update test for deleteUser
 - [x] Add cleanup SQL to legacy db update file (see [#1106](https://github.com/ezsystems/ezpublish-legacy/pull/1106) )


Closes #922