Custom graph layout

[wlandau]

Prework

• [x] Read and abide by drake's code of conduct.
• [x] Search for duplicates among the existing issues, both open and closed.

Description

For the graph visuals, the default Sugiyama layout does not look as good as the hierarchical layout, and we needed to get away from the hierarchical layout in order to solve #834. So I think it is time to impose custom x and y coordinates for the graph. Requirements:

• [ ] Distribute the y coordinates roughly according to their order in the plan.
• [ ] Respect the current horizontal leveling.
• [ ] Respect the current 1:1 aspect ratio, even for large graphs.

[wlandau]

Local experimentation shows that post-hoc hacks to y coordinates are only roughly respected in visNetwork graphs (e.g. graph$x$nodes$y). I am not sure about the proper way to do this.