feat: stats compute + summarize cardinality logic #97

Job	Run time
Test Spark (Scala 2.13.17) / batch_tests	4m 47s
Test Spark (Scala 2.13.17) / join_tests	3m 55s
Test Spark (Scala 2.13.17) / groupby_tests	2m 30s
Test Spark (Scala 2.13.17) / analyzer_tests	4m 15s
Test Spark (Scala 2.13.17) / fetcher_tests	4m 15s
Test Spark (Scala 2.13.17) / streaming_tests	3m 52s
Test Spark (Scala 2.13.17) / spark_tests	4m 13s
Test Spark (Scala 2.12.18) / spark_tests	4m 30s
Test Spark (Scala 2.12.18) / batch_tests	4m 55s
Test Spark (Scala 2.13.17) / kv_store_tests	1m 59s
Test Spark (Scala 2.13.17) / udafs_tests	2m 18s
Test Spark (Scala 2.12.18) / streaming_tests	3m 25s
Test Spark (Scala 2.13.17) / stats_tests	2m 47s
Test Spark (Scala 2.12.18) / join_tests	3m 59s
Test Spark (Scala 2.12.18) / kv_store_tests	1m 51s
Test Spark (Scala 2.12.18) / groupby_tests	2m 23s
Test Spark (Scala 2.12.18) / udafs_tests	2m 16s
Test Spark (Scala 2.12.18) / analyzer_tests	4m 6s
Test Spark (Scala 2.12.18) / stats_tests	2m 38s
Test Spark (Scala 2.12.18) / fetcher_tests	3m 27s
	1h 8m 21s

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