Add support for validation jobs to `sync.ts`, and refactor #2955

Job	Run time
Upload debug artifacts (default)	6m 0s
Upload debug artifacts (nightly-latest)	6m 0s
Upload debug artifacts (stable-v2.20.3)	6m 3s
Upload debug artifacts (linked)	5m 36s
Download and check debug artifacts	8s
	23m 47s

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