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/vue_shared/components/user_avatar/user_avatar_image.js

@@ -68,8 +68,7 @@ export default {
         v-if="!svg"
         :class="imgCssClasses"
         :src="imgSourceWithFallback"
-        :width="size"
-        :height="size"
+        :style="{ width: size + 'px', height: size + 'px' }"
         :alt="alt"
         :data-container="tooltipContainer"
         :data-placement="tooltipPlacement"