Add support for validation jobs to `sync.ts`, and refactor #9303

Job	Run time
Split workflow (ubuntu-latest, default)	1m 27s
Split workflow (macos-latest, linked)	2m 11s
Split workflow (macos-latest, nightly-latest)	2m 24s
Split workflow (ubuntu-latest, linked)	2m 0s
Split workflow (macos-latest, default)	1m 40s
Split workflow (ubuntu-latest, nightly-latest)	1m 10s
	10m 52s

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