Wall Street’s apprehension about the cost of developing artificial intelligence technology has been simmering beneath the surface of the stock market for months. Now it’s starting to boil over.Microsoft Corp. reported solid earnings on Wednesday, but investors zeroed in on stagnating growth in its Azure cloud-computing business and the more than $100 billion it’s expected to dole out in capital spending this year. The next day, the stock tumbled 10%, and the selling continued on Friday, wiping out $381 bil ...