[Feature request] Save and display "Last printed at" timestamp

[sorcerer]

I would like to have the firmware save the last print timestamp for all files and send it to Duet Web Control to be displayed in the Jobs list. Displaying it on the PanelDue would also be a nice touch if the available panel space allows for it.

This would make it easier to keep track of which files were printed or not out of a large assembly, such as a list of components for a 3D printer, without requiring the use of external tools.
It would also be helpful to save the last print state. That is whether the print was successful or failed/cancelled.

Maybe this could be added as a comment in the gcode file itself, similar to how the "Generated by" info is parsed and displayed.