LIKE BETTE DAVIS AND JOAN CRAWFORD, artists and fashion designers seem to work best together when the egos are thoroughly massaged and the contact is minimal. Perhaps that’s why their projects often take on a perfunctory air, stripped of the spontaneous spirit that collaboration is meant to elicit. Nearly every blue-chip artist, it seems, has had their name on a T-shirt or their imprint inscribed on a couture show. Designers, often under enormous pressure to puff up a modest house into a billion-dollar biz while retaining its cachet, regularly discover that a sure way to temper commerciality