Signage outside the Nasdaq MarketSite in New York on March 23, 2023.Stephanie Keith | Bloomberg | Getty ImagesWith second-quarter earnings from tech's mega-cap companies largely in the rearview mirror, one thing is clear: Wall Street is nervous.The Nasdaq slumped 3.4% this week, bringing its three-week slide to 8.8%. It's the worst performance for the tech-heavy index over that length of time since September 2022, when the market was in freefall due to soaring inflation and rising interest rates.Since the e ...