Debug utilities
We should provide test developers with some utilities they can use to access router in the middle of tests. The reason is to debug and manually test specific setup produced by tests.
NSFarm is designed so it is self terminating so there is no easy way to preserve state after its exit. The reason is that as a reboot and power supply control RST and CST pins of USB-to-TTL cable are used. Those are reverted to default state once program driving them exits. That program is NSFarm (pytest) process. One possibility, that we won't go by, is to have separate process that survives NSFarm exit optionally and holds terminal. This would require some additional communication protocol to be introduced between such program and NSFarm. The different option (and probably also more intuitive) is that we provide developers with routines that would be run as part of NSFarm and allowed them in specific exact code line to pause execution and to get control of serial console. Why serial console and not anything else is because everything else can be accessed in duplicity (connect to container or ssh to board from container).