View comments and system notes real-time edits (but not deletes)

Resources

FE @MadLittleMods

• Comment updates are currently not updated in real-time. They should be.
• Their transitions should follow the GitLab UX guide standard of quick update: https://docs.gitlab.com/ee/development/ux_guide/animation.html#quick-update
• Follow up to https://gitlab.com/gitlab-org/gitlab-ce/issues/29977.
• Real-time deletes are out of scope for this issue.