Support requesting latest nightly with `tools: nightly` #5083

Job	Run time
Diagnostic export (ubuntu-latest, linked)	46s
Diagnostic export (macos-latest, linked)	53s
Diagnostic export (windows-latest, nightly-latest)	57s
Diagnostic export (macos-latest, nightly-latest)	54s
Diagnostic export (ubuntu-latest, nightly-latest)	53s
Diagnostic export (windows-latest, linked)	55s
	5m 18s

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