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/stylesheets/framework/icons.scss

@@ -65,9 +65,7 @@
   }
 }
-.user-avatar-link {
-  text-decoration: none;
-}
+.user-avatar-link,
 .avatar-image-container {
   text-decoration: none;
-}
\ No newline at end of file
+}