Add support for deferred links in persistent user callouts.

What does this MR do?

Persistent user callouts now support deferred links, which are links that can be used to dismiss the callout, and then proceed to follow the link's original location.

This ensures that the callout dismissal is properly recorded before the user leaves the page.

This is needed for the privacy policy update that we're showing users https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/30808

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Separation of EE specific content

Performance and testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

Closes #64341 (moved)