Implement chaos testing framework

[jpsamaroo]

As the scheduler grows more optimizations, options, and supported features, the combination of configurations that the scheduler needs to handle correctly grows exponentially. We could do ourselves a great service by doing automated testing of random configurations as part of CI. We could also do fault injection if this works out well.

Parameters that would vary:

• DAG size and shape
• Anonymous and named function thunks
• Thunk/Scheduler options
• Processor types (ThreadProc for now)
• Checkpointing
• Dynamic DAG extension and querying
• SIGINT handling

Some metrics we'd want to test:

• Correctness
• Total runtime length
• Per-process memory usage
• Caching statistics
• Network transfer statistics
• Visualization output