Allow pinless chips with a prop

[seveibar]

e.g. noPorts or noPins to indicate we should not throw an error if a chip has no ports

[homie-gg[bot]]

Here are some pull requests that might be helpful reference for this task:

• make pinLabels and schPortArrangement optional
• add hack allowing missing start_pcb_port_ids and end_pcb_port_ids to not break overlap testing when a trace only contains two ports
• Chip Implementation