Add popover for branch modification setting

What does this MR do and why?

Add popover for branch modification setting

• add learn more link
• add button to permanently dismiss the popover
• add tests

Changelog: added

EE: true

Screenshots or screen recordings

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

Before	After
No popover

How to set up and validate locally

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

echo "Feature.enable(:scan_result_policy_settings)" | rails c

1. Upload a GitLab Ultimate license
2. Navigate to a project/group => Secure => Policies => New policy => Scan Result Policy
3. Verify "All protected branches" is selected by default and the Prevent branch protection modification setting is selected
4. Deselect Prevent branch protection modification
5. Verify popover appears
6. Switch from "All protected branches"
7. Verify popover disappears
8. Switch back to "All protected branches"
9. Verify popover appears
10. Select the checkbox
11. Verify popover disappears
12. Navigate to yaml mode, switch yaml to disable the setting, navigate back to rule mode
13. Verify the popover appears
14. Click the Learn more link
15. Verify user is navigated to https://docs.gitlab.com/ee/user/application_security/policies/scan-result-policies.html
16. Click the Don't tell me this again button
17. Verify user is never notified again

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.

Related to #418766 (closed)