feat: stats compute + summarize cardinality logic #98

Job	Run time
Test Spark (Scala 2.13.17) / spark_tests	3m 43s
Test Spark (Scala 2.13.17) / fetcher_tests	4m 16s
Test Spark (Scala 2.13.17) / batch_tests	4m 56s
Test Spark (Scala 2.13.17) / join_tests	4m 0s
Test Spark (Scala 2.13.17) / streaming_tests	3m 34s
Test Spark (Scala 2.13.17) / kv_store_tests	1m 58s
Test Spark (Scala 2.13.17) / analyzer_tests	4m 21s
Test Spark (Scala 2.13.17) / udafs_tests	2m 19s
Test Spark (Scala 2.13.17) / stats_tests	2m 46s
Test Spark (Scala 2.13.17) / groupby_tests	2m 33s
Test Spark (Scala 2.12.18) / join_tests	3m 57s
Test Spark (Scala 2.12.18) / fetcher_tests	4m 9s
Test Spark (Scala 2.12.18) / analyzer_tests	4m 8s
Test Spark (Scala 2.12.18) / groupby_tests	2m 25s
Test Spark (Scala 2.12.18) / streaming_tests	3m 36s
Test Spark (Scala 2.12.18) / udafs_tests	2m 8s
Test Spark (Scala 2.12.18) / spark_tests	3m 45s
Test Spark (Scala 2.12.18) / batch_tests	4m 41s
Test Spark (Scala 2.12.18) / stats_tests	2m 42s
Test Spark (Scala 2.12.18) / kv_store_tests	1m 50s
	1h 7m 47s

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