A wave of high-profile, class-action lawsuits and settlements this summer has raised allegations of race and sex discrimination in pay and promotion at some of the nation’s best-known corporations, a list that expanded yesterday to include retailer Costco Wholesale Corp. Last month, investment bank Morgan Stanley agreed to pay $54 million to settle claims that it underpaid and did not promote women. A few days later, aircraft manufacturer Boeing Co. agreed to pay up to $72.5 million to settle similar allegations. That same month, a group of black employees sued Eastman Kodak Co. accusing the company of systemic race discrimination, and an Alabama judge held a hearing on an ongoing race discrimination case against BellSouth Corp. In June, a federal judge ruled that a sex-discrimination case against Wal-Mart Stores Inc., the nation’s largest retailer, could proceed as a class action involving as many as 1.6 million women, although Wal-Mart has persuaded an appeals court to review the ruling.