Build and present a list of rat lines.
<p>
The first argument is either <i>view</i>, in which case the list is
presented on the GUI as a view list dialog, or <i>print</i> in which
case rat line coordinates are printed in the message log. The view dialog
approach allows quick navigation to the rat lines on GUI while the print
approach allows better CLI integration.
<p>
This action is provided to ease finding the last few remaining rat lines in
a dense mostly routed board and is typically invoked after rats nest
optimization (hotkey {c r} with the default menu file).