Throw an Error if level is ErrorLevel, add Logging.Debug as a Level

[jClugstor]

Checklist

• Appropriate tests were added
• Any code changes were done in a way that does not break public API
• All documentation related to code changes were updated
• The new code follows the
  contributor guidelines, in particular the SciML Style Guide and
  COLPRAC.
• Any new documentation only uses public API

Additional context

First, this makes it so that if the level is an ErrorLevel, emit_message will also throw an exception, after putting the Error message in to the log.

To be clear this means that

@SciMLMessage(message, verbose, :setting)

will put an error message in to the log, then throw an ErrorException, if verbose.setting is an ErrorLevel.

@ChrisRackauckas is that the desired behavior? I could also make it so that ErrorLevel has a Bool field, so users can choose to just send the message to the log and not throw an error.

Second, Logging.Debug is a thing, so it should be exposed and able to be used.

Also cleaned up the signature for emit_message, got rid of now unneeded arguments.

[ChrisRackauckas]

@ChrisRackauckas is that the desired behavior? I could also make it so that ErrorLevel has a Bool field, so users can choose to just send the message to the log and not throw an error.

Yes, the idea is "I want to know exactly when this thing is happening" can be done by turning that print into an error and then you'll be right there in the stack trace.

[ChrisRackauckas]

Second, Logging.Debug is a thing, so it should be exposed and able to be used.

I don't understand why "debug" would be lower than the others? What is that doing?