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

spec/javascripts/vue_shared/components/user_avatar_image_spec.js

@@ -21,11 +21,11 @@ describe('User Avatar Image Component', function () {
         },
         template: `
           <user-avatar-image 
-            :size='size' 
-            :src='src' 
-            :alt='alt' 
-            :css='css' 
-            :tooltip-text='tooltipText'>
+            :size="size" 
+            :src="src"
+            :alt="alt" 
+            :css="css"
+            :tooltip-text="tooltipText">
           </user-avatar-image>
         `,
       }).$mount();