emulator: fail-fast on provision errors, diagnose smoke test failures #3343

Job	Run time
Check if migrations changed	7s
No migration changes (skipped)	3s
Back-compat — Current branch migrations with ${{ needs.check-migrations-changed.outputs.base_branch }} branch code	-1s
Forward-compat — Current branch code with ${{ needs.check-migrations-changed.outputs.base_branch }} branch migrations	0s
	9s

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