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/boards/components/issue_card_inner.js

@@ -54,7 +54,6 @@ gl.issueBoards.IssueCardInner = Vue.extend({
     showLabelFooter() {
       return this.issue.labels.find(l => this.showLabel(l)) !== undefined;
     },
-
   },
   methods: {
     showLabel(label) {