feat: add experimental annotation #5533

Job	Run time
sample_operators_tests (sample-operators/mysql-schema)	2m 39s
sample_operators_tests (sample-operators/leader-election)	3m 21s
sample_operators_tests (sample-operators/webpage)	3m 7s
sample_operators_tests (sample-operators/tomcat-operator)	2m 42s
	11m 49s

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