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.js

@@ -70,10 +70,10 @@ export default {
         :title="tooltipText"
         ref="tooltipTarget"
       />
-      <span
+      <template
         v-if="svg"
         v-html="svg">
-      </span>
+      </template>
     </span>
   `,
 };