THE 1990 CHRYSLER Imperial is a work of macabre elegance. It is luxury a` la funeral parlor, the best of the Dracula House of Design. It is not a car that will appeal to anyone under 35 years old. Indeed, the thing is so brooding in its self-conscious formality, it is likely to scare away folks in their mid-forties, too. It's crazy. I mean, here is Chrysler's "flagship" automobile, its "elite entry in a highly competitive market segment," to quote the company's publicists. That means the Imperial is supposed to go against rides like the Nissan Infiniti Q-45, BMW 535i, Cadillac Eldorado Touring...