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

@@ -28,12 +28,6 @@ describe('User Avatar Image Component', function () {
       expect(this.userAvatarImage.$el.tagName).toBe('IMG');
     });
-    it('should return neccessary props as defined', function () {
-      _.each(this.propsData, (val, key) => {
-        expect(this.userAvatarImage[key]).toBeDefined();
-      });
-    });
-
     it('should properly compute tooltipContainer', function () {
       expect(this.userAvatarImage.tooltipContainer).toBe('body');
     });