test(buffer operator): execute tests with TestScheduler#run (#5055)
test(buffer operator): execute tests with TestScheduler#run (#5055)

* use TestScheduler#run for tests, align marbles inside string literals

* remove unused helper

* add missing space for linter

kwonoj/RxJS,ReactiveX/rxjs,martinsik/rxjs,ReactiveX/RxJS,ReactiveX/rxjs,benlesh/RxJS,kwonoj/RxJS,martinsik/rxjs,martinsik/rxjs,ReactiveX/rxjs,kwonoj/RxJS,ReactiveX/RxJS,trxcllnt/RxJS,benlesh/RxJS,ReactiveX/RxJS,trxcllnt/RxJS,trxcllnt/RxJS,benlesh/RxJS,ReactiveX/rxjs,benlesh/RxJS,martinsik/rxjs,trxcllnt/RxJS,kwonoj/RxJS,ReactiveX/RxJS