One way to do this would have been to keep the Uuids in the editor
copy. However, this opens us up to errors if we forget a Save As or
export path and end up writing the Uuids out somewhere else.
In the end, it felt safer to store a map of the original Uuids and
restore them if we happen to save the editor footprint back to the
board.
Fixes https://gitlab.com/kicad/code/kicad/issues/7312
Also fixes some latent bugs with not updating the local ratsnest
visibility in other places, and the netcode in update PCB from schematic.
Fixes https://gitlab.com/kicad/code/kicad/issues/7202
Jeff Young
Seth Hillbrand
Marek Roszko