Optimize DatabaseExportMetaDataGenerator, null value properties are not exported #13412

Job	Run time
Import Global Environment / init-environment	2s
Build E2E Image	6m 1s
E2E - Agent with MySQL (proxy, tracing, jaeger)	5m 44s
E2E - Agent with MySQL (proxy, tracing, zipkin)	5m 11s
E2E - Agent with MySQL (proxy, metrics, prometheus)	5m 34s
E2E - Agent with MySQL (proxy, logging, file)	5m 28s
E2E - Agent with MySQL (jdbc, logging, file)	5m 6s
E2E - Agent with MySQL (jdbc, metrics, prometheus)	5m 39s
E2E - Agent with MySQL (jdbc, tracing, jaeger)	5m 3s
E2E - Agent with MySQL (jdbc, tracing, zipkin)	5m 10s
	48m 58s

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