View ancestor line in epic sidebar

Current

• An issue can have a parent epic.
• An epic can have a parent epic.

Design

• So given an epic, view your ancestor line in the sidebar.
• For the first iteration, only the epic sidebar should have this tree. The issue sidebar should continue to show just the immediate parent, as it is (ux-research#134 (closed) and https://gitlab.com/gitlab-org/growth/issues/63 will aim to decrease the number of components in the issue sidebar)

header	header

• Position in sidebar- this section will replace Parent epic, so the order in the sidebar should be (top to bottom): Todo, Start date, Due date, Labels, Ancestors, Participants, Notifications
• Icons are Open and Closed
• Icons should be filled #1f78d1($blue-500) if the issue/epic is closed, and #1aaa55 ($green-500) if the issue/epic is open
• Each ancestor has 16px margin between them
• Connecting lines are #a7a7a7 ($gray-500)
• Recommendation- add the connecting lines as one solid line, like we do for the discussion/system notes connecting lines, rather than using pseudo-elements

End goal (when we have sub-issues and updated icons

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