Add confirmation input component

What does this MR do?

Adds the confirmation input component for Vue

This component is meant to be used in conjunction with the new modal component, allowing to have modals designed in this fashion to be implemented

Issues/Merge Requests that need this component as to not remain blocked https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16062 https://gitlab.com/gitlab-org/gitlab-ce/issues/42603

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• 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

P.S. All credit of this goes to @winh