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_link.js

@@ -38,7 +38,9 @@ export default {
     },
   },
   template: `
-    <a :href="href" class="user-avatar-link">
+    <a 
+      class="user-avatar-link"
+      :href="href">
       <user-avatar-image
         :src="imgSrc"
         :alt="imgAlt"