Make the team structure (org chart) page vertical

When your team is relatively flat (like ours) it makes a lot more sense for the org chart https://about.gitlab.com/team/structure to be vertical, like a hierarchical list.

See https://omextemplates.content.office.net/support/templates/en-au/lt00001013.png for an example.

This will also prevent people from having to scroll horizontally.

Please make sketch first before programming this.

/cc @luke @timzallmann

Final Design

Changes are awaiting approval in !6945 (merged)