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_link_spec.js

-/* eslint-disable no-restricted-syntax */
-
 import Vue from 'vue';
 import UserAvatarLink from '~/vue_shared/components/user_avatar/user_avatar_link';
 describe('User Avatar Link Component', function () {
   describe('Initialization', function () {
     beforeEach(function () {
-      const propsData = this.propsData = {
+      this.propsData = {
         href: 'myavatarurl.com',
         imgSize: 99,
         imgSrc: 'myavatarurl.com',
@@ -16,12 +14,12 @@ describe('User Avatar Link Component', function () {
       };
       this.vueInstance = new Vue({
-        data: propsData,
+        data: this.propsData,
         components: {
           'user-avatar-link': UserAvatarLink,
         },
         template: `
-          <user-avatar-link 
+          <user-avatar-link
             :href="href"
             :img-size="imgSize"
             :img-src="imgSrc"
@@ -63,12 +61,9 @@ describe('User Avatar Link Component', function () {
       expect(componentImgTag).toContain('<img');
     });
-    it('should return neccessary props as defined', function (done) {
-      Vue.nextTick(() => {
-        _.each(this.propsData, (val, key) => {
-          expect(this.userAvatarLinkComponent[key]).toBeDefined();
-        });
-        done();
+    it('should return neccessary props as defined', function () {
+      _.each(this.propsData, (val, key) => {
+        expect(this.userAvatarLinkComponent[key]).toBeDefined();
       });
     });
   });