SAN FRANCISCO — WeWork raised more than $11 billion in funding as a private company. Olive AI, a health care startup, gathered $852 million. Convoy, a freight startup, raised $900 million. And Veev, a home construction startup, amassed $647 million. In the last six weeks, they all filed for bankruptcy or shut down. They are the most recent failures in a tech startup collapse that investors say is only beginning. After staving off mass failure by cutting costs over the past two years, many once-p