[rigs] Add a system utilization rig

[TurboTurtle]

The process rig can monitor process(es) for state changes and resource consumption. We should have one that monitors total system resource consumption as well.

We should be able to do this with the psutil module as we did with process.

We should be able to monitor:

• cpu usage
• specific cpu substats like %steal
• total memory usage
• disk usage/activity

What I'm not sure of as being advantageous but is possible to monitor (how easily remains to be seen):

• load avg
• runq size
• temps/sensors

[TurboTurtle]

Resolved via 5ab8ed7