Legal tech startup Harvey is now valued at $15.6 billion after raising $550 million in a new funding round aimed at powering efforts to build its own AI models.The fundraise was co-led by Lightspeed Venture Partners and Diffusion, a new firm cofounded by longtime Harvey backer and former Coatue Management investor Kris Fredrickson. Sapphire Ventures and Whale Rock Capital Management, as well as a number of Harvey’s existing investors, also participated in the round....