Scheduled drift and patching runs for the Raspberry Pi fleet

The Raspberry Pi estate had no scheduled equivalent of the configuration-drift and patching runs the Ubuntu servers already get.

Two runs now exist and are chained so they can never overlap: the first converges configuration without touching packages, the second patches without touching configuration, and the second only starts if the first succeeded.

Overlap is the specific failure this prevents. A configuration run that reboots a machine while a patching run is mid-package is how a jump host was left unreachable earlier this month.