Convert `sync_back.py` to TypeScript #2836

Job	Run time
Upload debug artifacts (stable-v2.20.3)	5m 56s
Upload debug artifacts (nightly-latest)	5m 37s
Upload debug artifacts (default)	5m 49s
Upload debug artifacts (linked)	6m 16s
Download and check debug artifacts	8s
	23m 46s

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