Do not update/delete: Banner broadcast message test data
Do not update/delete: Notification broadcast message test data
Creates 3 vue components:
user-avatar-link
user-avatar-image
user-avatar-svg
and implements them in several places.
Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/31017
EE Compatible Branch: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1699
