Fix usage of `ActiveRecord::Tasks::DatabaseTasks.migrate` in `DatabaseCleaner` to properly support many databases (likely fixed upstream)
As part of PoC we identified that ActiveRecord::Tasks::DatabaseTasks.migrate
function does not properly migrate many databases.
We workaround that by copying and fixing this method:
- forcing disconnect to ensure that we don't have stale connections (in some cases we failed to run migrations due to another connection being open)
- iterate all DBs