Google’s proposed $23 billion acquisition of cloud security startup Wiz would help it compete with Microsoft, the top seller of security software. If the deal manages to avoid antitrust challenges and other hang-ups in the ongoing negotiations—and those issues are still a big if—it would also create a windfall for the startup’s investors during a period in which such returns have been lacking.Several venture capital firms, including Index Ventures, Sequoia Capital, Insight Partners, Greenoaks Ca...