Extract JumpToNextDiscussionButton component from NoteableDiscussion

This is part of https://gitlab.com/gitlab-org/gitlab-ce/issues/55566.

Extract this bit https://gitlab.com/gitlab-org/gitlab-ce/blob/8b4b7caefa7fba49a8b199edfde8315a4c897a68/app/assets/javascripts/notes/components/noteable_discussion.vue#L464-473 into a new JumpToNextDiscussionButton component.