Add kafkaBatchSize configuration field

Avoids the default 1 second delay when the batch doesn't
reach 100 messages within that time.

Useful when the Kafka exporter is not cached, as it would
otherwise encounter that delay. Setting BatchSize to 1
prevents this.

ees/kafka.go

@@ -88,6 +88,10 @@ func NewKafkaEE(cfg *config.EventExporterCfg, dc *utils.SafeMapStorage) (*KafkaE
 		},
 	}
 
+	if opts.BatchSize != nil {
+		pstr.writer.BatchSize = *opts.BatchSize
+	}
+
 	return pstr, nil
 }