Migrate milestones empty state component to Pajamas

What does this MR do and why?

Migrate milestones empty state to Pajamas component

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Create a new project within flightjs
2. Go to http://gdk.test:3000/flightjs/your-project-name/-/milestones
3. See empty state
4. Go to http://gdk.test:3000/admin/users/
5. Choose any user with 0 projects and 0 groups, for example http://gdk.test:3000/admin/users/reported_user_9
6. Click [Impersonate] in the right top corner of the page
7. Go to http://gdk.test:3000/dashboard/milestones
8. See empty state
9. Click on the person with a hat and the glasses icon near the user avatar in the menu bar to stop impersonating
10. Go to http://gdk.test:3000/flightjs/Flight/-/milestones?search_title=ddd&state=all&sort=due_date_desc
11. See empty state

#457239