Many more tables have indexes with the same names which can cause issues
on SQLite/Postgres. Also, add an option for migrations to rename indexes.
PHPBB-17525
The migration helper currently drops any keys with schema changes that have
the data_depth 1. This change will correctly assign the keys to the steps
array without dropping the keys that might contain important info like the
actual table that should be created.
PHPBB3-12170
