scheduler: sort gang of same gangGroup by gangId #7524

Job	Run time
golangci-lint	59s
unit-tests(Check Go modules)	38s
unit-tests(Check manifests)	42s
unit-tests(Check auto-generated codes)	4m 57s
unit-tests(Verify gofmt)	36s
unit-tests(Verify govet)	50s
unit-tests(Run Go build)	1m 59s
unit-tests(Run Go test)	5m 48s
build-and-push (koordlet)	3m 3s
build-and-push (koord-manager)	2m 25s
build-and-push (koord-scheduler)	3m 1s
build-and-push (koord-descheduler)	3m 49s
	28m 47s

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