Trigger `project_update` system hook when archiving projects

What does this MR do?

System hooks are not triggered by project archive and unarchive events. These hooks should be triggered. Reuse the Projects::UpdateService to trigger the project_update hook, as proposed by @DouweM https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16610#note_58437269

Testing:

• Archive/Unarchive works via interface
• Archive/Unarchive works via API
• Verify system hooks fire

{"event_name":"project_update","created_at":"2018-08-02T19:32:04Z","updated_at":"2018-08-02T20:09:17Z","name":"archive-test-foo","path":"archive-test-foo","path_with_namespace":"jramsay/archive-test-foo","project_id":15,"owner_name":"James Ramsay","owner_email":"test@example.com","project_visibility":"public"}

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

• Archive/Unarchive works via interface
• Archive/Unarchive works via API
• Verify system hooks fire

Why was this MR needed?

System hooks are useful and should be triggered by important events in the project lifecycle, like project archive/unarchive.

Screenshots (if relevant)

n/a – no visible changes

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Conforms to the code review guidelines
  • Has been reviewed by a UX Designer
  • Has been reviewed by a Frontend maintainer
  • Has been reviewed by a Backend maintainer
  • Has been reviewed by a Database specialist
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• If you have multiple commits, please combine them into a few logically organized commits by squashing them
• Internationalization required/considered
• End-to-end tests pass (package-and-qa manual pipeline job)

What are the relevant issue numbers?

https://gitlab.com/gitlab-org/gitlab-ce/issues/42275