Added user-callouts

What does this MR do?

Adds a user callout to the dashboard/projects and /{current_user} routes, which vanishes and doesn't come back as soon as you hit the Check it out button or the x icon

The check it out button should take you the current user /profile/preferences route

Are there points in the code the reviewer needs to double check?

None at the moment

Screenshots (if relevant)

/{current_user}

/dashboard/projects

Mobile

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

closes #27269 (closed)

EE Merge Request

https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1266

\cc @awhildy