Fixes KafkaEmitter not emitting queryType for a native query. The Event to JSON serialization was extracted to the external class: EventToJsonSerializer. This was done to simplify the testing logic for the serialization as well as extract the responsibility of serialization to the separate class.
The logic builds ObjectNode incrementally based on the event .toMap method. Parsing each entry individually ensures that the Jackson polymorphic annotations are respected. Not respecting these annotation caused the missing of the queryType from output event.
* remove use of mocks for ServiceMetricEvent
* simplify KafkaEmitterTests by moving to Mockito
* speed up KafkaEmitterTest by adjusting reporting frequency in tests
* remove unnecessary easymock and JUnitParams dependencies