BUGFIX: prevent creating new alias for columns after filters changed

[danfraticiu]

As described in issue 12225

When there is a oneToMany relation where the children use single table inheritance, if the relation is re-fetched after a filter changed, SingleTablePersister::getSelectColumnsSQL will generate new aliases for the child entity fields. Then ResultSetMapping::addIndexBy picks the first alias that matches the indexBy field, which doesn't exist in the updated list. This causes ObjectHydrator:502 to throw an ErrorException: Warning: Undefined array key

This PR prevent creating new aliases.

The change is inspired by the code in BasicEntityPersister::getSelectColumnSQL which reuses the aliases that already exist.