Change EventState and ArtifactBuildState enums back to single int representation again.
    
    As part of monitor code, the enum values for EventState and ArtifactBuildState have been
    changed to (int, counter) format. This made the code like EventState(0) not working, because
    Enum class only knew '(0, None)' enum value, not just '0'.
    
    This commit changes Enum values back to integer and sets 'counter' in __init__ method
    of both enum subclasses.
    
    This commit also fixes monitor tests in test_monitor.py.