This uses the feature flag and work in
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/56509 to ensure
the query planner chooses the nested join instead of the more expensive
hashed join. When the `use_distinct_for_all_object_hierarchy` feature
flag is used globally, it will apply to all queries, not just the ones
that have manually enabled them via the `options` hash while creating
`ObjectHierarchy`.

This change works around a PostgreSQL query planner bug that is detailed
in https://gitlab.com/gitlab-com/gl-infra/production/-/issues/3894.

Related issues:

1. https://gitlab.com/gitlab-com/gl-infra/production/-/issues/4024
2. https://gitlab.com/groups/gitlab-org/-/epics/5617