improve: add sharding sample as integration test #7386

Job	Run time
sample_operators_tests (sample-operators/webpage)	3m 48s
sample_operators_tests (sample-operators/mysql-schema)	3m 44s
sample_operators_tests (sample-operators/leader-election)	4m 40s
sample_operators_tests (sample-operators/tomcat-operator)	3m 51s
sample_operators_tests (sample-operators/operations)	9m 3s
	25m 6s

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