improve: PrimaryUpdateAndCacheUtils locks, naming and doc improvements #5163

Job	Run time
sample_operators_tests (sample-operators/tomcat-operator)	2m 42s
sample_operators_tests (sample-operators/mysql-schema)	2m 52s
sample_operators_tests (sample-operators/leader-election)	3m 21s
sample_operators_tests (sample-operators/webpage)	3m 7s
	12m 2s

Provide feedback