View real-time updates for merge request widget

• Once https://gitlab.com/gitlab-org/gitlab-ce/issues/25424 (Vue refactor of widget) is complete, we can make the widget itself real-time.
• Statuses and information in the widget should be updated in real time.
• Need to determine the styling of the updates. What type of CSS transition? Do we do the same transition as the one in here? https://gitlab.com/gitlab-org/gitlab-ce/issues/29977
• Should all elements update at the same interval?