Consolidate user avatar Vue logic

Creates 3 vue components:

1. user-avatar-link
2. user-avatar-image
3. user-avatar-svg

and implements them in several places.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/31017

• Port to EE
• Test each implementation manually

EE Compatible Branch: https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1699

spec/javascripts/vue_shared/components/user_avatar_image_spec.js

@@ -4,7 +4,7 @@ import UserAvatarImage from '~/vue_shared/components/user_avatar/user_avatar_ima
 describe('User Avatar Image Component', function () {
   describe('Initialization', function () {
     beforeEach(function () {
-      const propsData = this.propsData = {
+      this.propsData = {
         size: 99,
         src: 'myavatarurl.com',
         alt: 'mydisplayname',