Luxury shoppers are getting wealthier and younger, with purchases by some of the newest consumers expected to grow three times faster than older generations over the next decade, according to a new report. Generation Y, also known as millennials, and Generation Z accounted for all of the luxury market's growth last year, according to a report from Bain & Co. Spending by Gen Z and the even younger Generation Alpha, or those under 13, is expected to make up a third of the luxury market through 2030, reflecting "a more precocious attitude toward luxury" among the younger ranks than older…