Moves author components into vue files

What does this MR do?

Moves more mr widget components into vue files Removes unused props Adds better tests cases

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by Frontend
• 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?

#34371 (moved) https://gitlab.com/gitlab-org/gitlab-ce/issues/41582