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_svg_spec.js

@@ -22,8 +22,8 @@ describe('User Avatar Svg Component', function () {
     });
     it('should have <svg> as a child element', function () {
-      const avatarSvgElement = this.userAvatarSvg.$el.innerHTML;
-      expect(avatarSvgElement).toContain('<path');
+      expect(this.userAvatarSvg.$el.tagName).toEqual('svg')
+      expect(this.userAvatarSvg.$el.innerHTML).toContain('<path');
     });
     it('should return neccessary props as defined', function () {