improve: integration test for PerResourcePollingEventSource delete event propagation #6750

Job	Run time
sample_operators_tests (sample-operators/mysql-schema)	2m 33s
sample_operators_tests (sample-operators/leader-election)	3m 22s
sample_operators_tests (sample-operators/webpage)	3m 9s
sample_operators_tests (sample-operators/metrics-processing)	7m 49s
sample_operators_tests (sample-operators/tomcat-operator)	2m 42s
	19m 35s

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