Optimize ShardingStatisticsTableCollector to support aggregated datasource #13306

Job	Run time
Import Global Environment / init-environment	3s
Build E2E Image	8m 4s
E2E - Agent with MySQL (proxy, tracing, jaeger)	6m 38s
E2E - Agent with MySQL (proxy, tracing, zipkin)	6m 45s
E2E - Agent with MySQL (proxy, metrics, prometheus)	6m 53s
E2E - Agent with MySQL (proxy, logging, file)	6m 25s
E2E - Agent with MySQL (jdbc, logging, file)	6m 28s
E2E - Agent with MySQL (jdbc, metrics, prometheus)	7m 9s
E2E - Agent with MySQL (jdbc, tracing, jaeger)	6m 26s
E2E - Agent with MySQL (jdbc, tracing, zipkin)	6m 32s
	1h 1m 23s

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