Add support for validation jobs to `sync.ts`, and refactor #9224

Job	Run time
Split workflow (ubuntu-latest, default)	1m 6s
Split workflow (ubuntu-latest, nightly-latest)	1m 17s
Split workflow (macos-latest, default)	1m 33s
Split workflow (macos-latest, nightly-latest)	1m 23s
Split workflow (macos-latest, linked)	1m 33s
Split workflow (ubuntu-latest, linked)	1m 28s
	8m 20s

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