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/pipelines_table_row_spec.js

@@ -102,7 +102,7 @@ describe('Pipelines Table Row', () => {
       }
       const commitAuthorLink = commitAuthorElement.getAttribute('href');
-      const commitAuthorName = commitAuthorElement.querySelector('img.avatar').getAttribute('title');
+      const commitAuthorName = commitAuthorElement.querySelector('img.avatar').getAttribute('data-original-title');
       return { commitAuthorElement, commitAuthorLink, commitAuthorName };
     };