* Add mock scripts for development
This enables TinyPilot developers to mock out two privileged functions during development:
* Change hostname
* Collect debug logs
Once the developer enables mock scripts on their system, they can use these two features and have it work (sort of) like it works on a real device.
This still leaves a few functions unmocked:
* Shutdown/restart (because we call those by absolute path to system scripts, we can't mock them out)
* Update: The update logic is pretty complex and involves launching a systemd process, so it's non-trivial to mock this out.
Related: #501
* Handle case where /opt/tinypilot-privileged is a real directory
