slo-controller: refactor codes for reading #7435

Job	Run time
golangci-lint	1m 45s
unit-tests(Check Go modules)	38s
unit-tests(Check manifests)	52s
unit-tests(Check auto-generated codes)	4m 28s
unit-tests(Verify gofmt)	1m 11s
unit-tests(Verify govet)	55s
unit-tests(Run Go build)	2m 8s
unit-tests(Run Go test)	5m 54s
build-and-push (koordlet)	3m 0s
build-and-push (koord-manager)	2m 50s
build-and-push (koord-scheduler)	2m 47s
build-and-push (koord-descheduler)	2m 35s
	29m 3s

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