In just over a year, artificial intelligence startup Harvey raised three investment rounds to develop software that takes the drudgery out of legal paperwork. Now the company wants an even bigger war chest—one that could help it acquire other companies.The San Francisco startup has been talking to investors about raising $600 million at a valuation of at least $2 billion, more than double its valuation from a December financing, according to a person involved in the discussions. If it’s able to ...