Add elastic backfill migration for internal notes

Nicolas Dularrequested to merge
nd/backfill-internal-notes-on-elastic into master

What does this MR do and why?

Adds the migration to backfill internal field for notes.

Issue: #387945 (closed)

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

Merge request reports