[ticket/13238] Add array implementation of tools so we can check sql_*_exists

PHPBB3-13238
[ticket/13238] Use array implementation of db\tools to generate the schema

PHPBB3-13238
[ticket/13360] Correctly drop unique keys with db\tools

PHPBB3-13360
[ticket/13238] Fix test to use db\tools_array

PHPBB3-13238