Some updates based on the test file.

[samitbasu]

Hello! I needed some updates to handle a 6 layer board and ran into a couple of other issues (the solid fill on the circle). The file was generated with KiCad 6, but still has the version 4 PCB format. Also, my editor automatically runs the code through rustfmt - so the diff is unnecessarily large. If you want me to trim it back to the bare minimum, I can do so.