Add the Log Level to the BudgetTrackingEvent itself

[baruchiro]

I think it would be cleaner to add the level to the BudgetTrackingEvent itself, setting it by default to INFO and having error set it to ERROR. Then you won't need this class and can use the event publisher directly.

In the current implementation you don't have access to the full api of the emitter which is useful (see comment about the option to set the status by listening to events)

Originally posted by @brafdlog in https://github.com/brafdlog/budget-tracking/pull/110#discussion_r502924382

[baruchiro]

Maybe this issue is actually about/depends on moving to events payload as classes.