Apple Inc., aiming to boost sluggish computer sales, is preparing to overhaul its entire Mac line with a new family of in-house processors designed to highlight artificial intelligence.The company, which released its first Macs with M3 chips five months ago, is already nearing production of the next generation — the M4 processor — according to people with knowledge of the matter. The new chip will come in at least three main varieties, and Apple is looking to update every Mac model with it, said...