Merge branch 'nd/confidential-to-internal-notes-bg-migration' into 'master'

Backfill internal column on notes

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/98433



Merged-by: Matthias Käppler <mkaeppler@gitlab.com>
Approved-by: Aman Luthra <aluthra@gitlab.com>
Approved-by: Steve Abrams <sabrams@gitlab.com>
Approved-by: Matthias Käppler <mkaeppler@gitlab.com>
Co-authored-by: Nicolas Dular <ndular@gitlab.com>