Improve build set graph display

• Investigate library options to save time here
  • egui-graphs provides a much better interactive view for large build set graphs.
  • cytoscape.js is mature and well-maintained, has no other dependencies such as react, and is less of an innovation token than a WASM project.
• Look into showing realtime updates without reloading an iframe, but don't invest a lot of time.

A few features we'd like:

• Space-efficient layout. graphs with lots of nodes should take up the minimum necessary space on screen
• Interactive node filtering:
  • Filter only transitive dependencies of a given node (e.g. "which packages will need to be rebuilt because of this package?")
  • Show only path from origin changeset(s) to a given node (e.g. "how did this package get into this graph?")