feat: add experimental annotation #5286

Job	Run time
sample_operators_tests (sample-operators/leader-election)	3m 19s
sample_operators_tests (sample-operators/webpage)	2m 55s
sample_operators_tests (sample-operators/mysql-schema)	2m 44s
sample_operators_tests (sample-operators/tomcat-operator)	2m 53s
	11m 51s

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