#28481: Display time tracking totals on milestone page

What does this MR do?

Implements #28481 (closed)

It shows the time tracking in milestone page's sidebar

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

Yes: unfortunately I am not good in Ruby nor Vue.

1. Is that the correct approach to inject a Vue component?
2. What is rootPath required by TimeTracker?
3. Where is the old template for the milestone time tracker? I suppose I need to delete that

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered
• End-to-end tests pass (package-qa manual pipeline job)

What are the relevant issue numbers?

#28481 (closed)