Add system notes for automatic rollups

What does this MR do and why?

Adds systems notes to parent work items when their progress is changed via rollup logic. MR to add rollup logic - !108461 (merged)

Ref - gitlab-org/incubation-engineering/okr/meta#24 (closed)

Screenshots or screen recordings

How to set up and validate locally

1. Open rails console by running bin/rails console within GDK directory.
2. Enable the feature flag :hierarchy_db_restrictions on a project; Feature.enable(:hierarchy_db_restrictions).
3. Enable the feature flag :okrs_mvc on the same project; Feature.enable(:okrs_mvc).
4. Enable the feature flag :okr_automatic_rollups on the same project; Feature.enable(:okr_automatic_rollups).
5. Visit issues list page for the project by navigating to http://gdk.test:3000/gitlab-org/gitlab-test/-/issues.
6. Create an objective by clicking on dropdown button next to New issue and selecting New objective from the dropdown.
7. Once objective is created, click on it to visit its Work Item page, you should be able to see Tree View below the description.
8. Use Add dropdown button create/add key results. 1.Try changing the progress for the Objective and you should see the help note with text about the info regarding progress rollups
9. Click on any KR to go to it's page and change it's progress and go back to its objective page to see the updates progress
10. Refresh the page to see system notes

MR acceptance checklist

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

• I have evaluated the MR acceptance checklist for this MR.