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

config/webpack.config.js

@@ -87,4+87,4 @@
       {
         test: /\.svg$/,
         loader: 'raw-loader',
       },
       {
         test: /\.(gif|png)$/,
         loader: 'url-loader',
-        query: { mimetype: 'image/gif' },
+        options: { limit: 2048 },
       },
       {
         test: /\.(worker\.js|pdf)$/,