Make sure data is copied to the landed filesystem if a reboot occurs

[AngusJull]

If the system reboots mid-flight, we should make that the flight logs that were left from before the reboot are also copied to the landed filesystem upon the landing of the rocket. Right now, the system will create new logging files on the power safe filesystem and only copy these upon landing, meaning we would seemingly lose part of the flight data. We should also check other reboot scenarios, like a reboot when landed.

[linguini1]

Can we just make it bulk-copy all files from pwrfs to usrfs on landing?

[AngusJull]

We might need to consider cleaning up previous flights, since we could have 30s of data from each time the system powered on. But overall I think that's a good idea

[linguini1]

If I can get the USB shell working I can add a command to wipe the partitions.