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

@@ -113,7 +113,6 @@ gl.issueBoards.IssueCardInner = Vue.extend({
         <user-avatar-link v-if='assigneeUrl'
           class='card-assignee js-no-trigger'
           :href='assigneeUrl'
-          :title='avatarUrlTitle'
           :img-alt='avatarUrlTitle'
           :img-src='issue.assignee.avatar'
           :img-size='20'