Remove nested logging interfaces for the AgroalLogger

The AgroalLogger has nested interfaces which don't seem to be uploadable to Zanata. The issue being the URL doesn't seem to be escaped properly given the name AgroalLogger$DriverLogger.i18n.properties. My assumption would be the $ isn't escaped.

That being said there is no reason to have nested interfaces. Different categories can be used to achieve the same concept. This also reduces the number of class objects needed to be defined.