Add support for validation jobs to `sync.ts`, and refactor #2983

Job	Run time
Upload debug artifacts (stable-v2.20.3)	5m 35s
Upload debug artifacts (linked)	5m 57s
Upload debug artifacts (nightly-latest)	5m 40s
Upload debug artifacts (default)	5m 47s
Download and check debug artifacts	7s
	23m 6s

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