Refactor DropSchemaPushDownMetaDataRefresher #13896

Job	Run time
Import Global Environment / init-environment	4s
Build E2E Image	5m 57s
E2E - Agent with MySQL (proxy, tracing, jaeger)	5m 44s
E2E - Agent with MySQL (proxy, tracing, zipkin)	5m 33s
E2E - Agent with MySQL (proxy, metrics, prometheus)	5m 38s
E2E - Agent with MySQL (proxy, logging, file)	5m 32s
E2E - Agent with MySQL (jdbc, logging, file)	5m 15s
E2E - Agent with MySQL (jdbc, metrics, prometheus)	5m 17s
E2E - Agent with MySQL (jdbc, tracing, jaeger)	5m 26s
E2E - Agent with MySQL (jdbc, tracing, zipkin)	5m 33s
	49m 59s

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