feat(run): Add labgrid verbosity options

Add support to run.py for enabling logging from Labgrid.

With the --log-level argument you can enable different levels (default is ERROR), these can also be controlled by setting a LOG_LEVEL environment variable.

By setting the level to DEBUG, you also turn on additional logging from the Labgrid StepLogger:

INFO         StepLogger:  → SSHDriver.run(cmd='cd /tmp/tmp.HeiAjaLHcj/execroot && /tmp/tmp.HeiAjaLHcj/execroot/env  /tmp/tmp.HeiAjaLHcj/execroot/ls') 
INFO         StepLogger:  ← SSHDriver.run() result=(['env', 'ls', 'ls.runfiles'], [], 0) [0.428s]