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

@@ -36,14 +36,14 @@ export default {
     },
   },
   template: `
-    <a :href='href'>
+    <a :href="href">
       <user-avatar-image
-        :src='imgSrc'
-        :svg='imgSvg'
-        :alt='imgAlt'
-        :css='imgCss'
-        :size='imgSize'
-        :tooltip-text='tooltipText'>
+        :src="imgSrc"
+        :svg="imgSvg"
+        :alt="imgAlt"
+        :css="imgCss"
+        :size="imgSize"
+        :tooltip-text="tooltipText">
       </user-avatar-image>
     </a>
   `,