This is based on the solution we created in
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/57830 to
improve the performance of the `Issuable::DestroyService`.

Previously, the associated `label_links` to an Issuable (can be a
MergeRequest, Issue or Epic) gets destroyed when an issuable gets
destroyed. If there are 100 label links, that means 100 delete
SQL queries as well.

With this fix, the deletion will be done in batches. It's being
done in batches to avoid statement timeouts in case there are a
lot of label links to be deleted.

The worker will be performed asynchronously when the feature flag
is enabled.

Changelog: performance