Cabana: Save/load signal charts layout

[paper5590]

Hi,

I suggest the ability to save/load signal charts layout, similar to PlotJuggler, so I can quickly switch routes and have all the signals I'm interested in shown.

[deanlee]

This was actually one of the features explored very early in Cabana’s development. There was even a PR for it at the time: (closed) #26186

We’ll need to find a cleaner and more maintainable approach before bringing it back.