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

app/assets/javascripts/vue_shared/components/user_avatar/user_avatar_image.vue

@@ -39,14 +39,11 @@ export default {
     },
   },
   computed: {
-    tooltipClass() {
-      return this.tooltipText ? 'has-tooltip' : '';
-    },
     tooltipContainer() {
       return this.tooltipText ? 'body' : null;
     },
     imgCssClasses() {
-      return `avatar ${this.tooltipClass} ${this.avatarSizeClass} ${this.cssClasses}`;
+      return `avatar ${this.avatarSizeClass} ${this.cssClasses}`;
     },
   },
 };