Basic support for overlay databases #3894

Job	Run time
Diagnostic export (ubuntu-latest, linked)	1m 8s
Diagnostic export (macos-latest, linked)	1m 15s
Diagnostic export (macos-latest, nightly-latest)	1m 10s
Diagnostic export (windows-latest, nightly-latest)	3m 37s
Diagnostic export (windows-latest, linked)	3m 2s
Diagnostic export (ubuntu-latest, nightly-latest)	1m 2s
	11m 14s

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