Introduce shared Vue component for pipeline jobs

Follow-up from https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/22505#note_110749674:

JobContainerItem and JobItem are very similar.

However currently both components are incompatible because:

• JobItem has an action button
• JobContainerItem has an icon for retried jobs
• JobContainerItem has custom styles applied that break JobItem

They should be split up and use a shared component.