We need to wait for atfwd_daemon to startup before sending any AT
commands, and I can't think of a way to reliably do that within rust.
So, instead of trying to switch the device to command mode before
executing a command, require the user to run the "--root" step
beforehand, and then start executing AT commands.
Add tools for launching a root shell on the device, and for sending
serial commands to the device. Extend the make.sh script to push those
and configure a root shell. Commands can now be executed as root via:
adb shell rootshell -c \"touch /tmp/test\"
allowing automatic configuration of the tooling.
