reset bootstrap progress when enough things change
Right now, setting DisableNetwork=1 doesn't reset the bootstrap progress indicator. It probably should, because all network connections to bridges or relays will close. This will improve the user experience once we have #27103 (moved) in place, because then the earlier progress shown will be the initial network connection that everything else depends on.
We probably also want to reset the bootstrap progress when a configuration change causes us to disconnect from all our guards.