[CN-Exec] Add logging levels to runtime library

[ZippeyKeys12]

In the case of random testing, I don't think we want all of these logs, except for a failing input.

Instead I think we want to:

• disable logging
• test many random inputs
• if we find a failing one
  • re-enable logging at the error level
  • rerun the failing input
• we allow the user to re-run it again with the full logs

[rbanerjee20]

This looks good, but I think we do want a debug level where we can see all the print statements as we are currently seeing them, which we would probably want to be configurable as a CLI option. I think this would be quite a bit more work though, since connecting up parts of the runtime library with the generated output seems less straightforward than just modifying the runtime library directly

[ZippeyKeys12]

I'm not sure I understand, the default logging level CN_LOGGING_INFO shows all the current print statements. Do you mean also exposing the ability to change the logging level via the cn instrument command? If so, that should be easy to do, I can add it.