Adding sync approach for Kafka in Emitter and Extension

Kafka events are currently published asynchronously. This Jira will add a property that allows an user to switch publishing to sync approach for Emitter and Extension (this is already available for work item handler). Default behaviour (in the absence of the property or when property is not set to true) will still be async

Property for kafka extension is org.kie.server.jbpm-kafka.ext.sync.

Property for kafka emitter is org.kie.jbpm.event.emitters.kafka.sync