Refactor the delete branch and delete protected branches from HAML to vuejs

What does this MR do?

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

Probably the deletion of the spinach test to delete a branch, explanation on the diff

Why was this MR needed?

To help correct a bug that I encountered on this MR https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16437, once this is merged, the aforementioned MR will be good for review/merge

Screenshots (if relevant)

Deleting a normal branch

Before	After

Deleting a protected branch

Before	After

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Closes #42603 (moved)