Add support for validation jobs to `sync.ts`, and refactor #9351

Job	Run time
Split workflow (macos-latest, default)	1m 28s
Split workflow (ubuntu-latest, nightly-latest)	1m 21s
Split workflow (ubuntu-latest, linked)	1m 32s
Split workflow (macos-latest, linked)	2m 6s
Split workflow (ubuntu-latest, default)	1m 24s
Split workflow (macos-latest, nightly-latest)	2m 53s
	10m 44s

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