feat: allow overriding test infrastructure kube client separately (#2… #5492

Job	Run time
sample_operators_tests (sample-operators/webpage)	3m 21s
sample_operators_tests (sample-operators/tomcat-operator)	2m 54s
sample_operators_tests (sample-operators/mysql-schema)	2m 44s
sample_operators_tests (sample-operators/leader-election)	3m 20s
	12m 19s

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