Cirrus Dependency Visualization

Cirrus task dependencies make my brain spin, so I wrote a quick tool to use graphviz for a simple diagram. Here's what we have as of 2021-02-01, reflecting the "Cirrus 2.0" structure (#6784) plus subsequent fixes.

<iframe src="cirrus-map.svg" allowfullscreen="true" height="600px" width="90%"></iframe>