By James Davey LONDON (Reuters) – Steve Rowe will next week step down as chief executive of British retailer Marks & Spencer after a turbulent six years in the top job, with his internal successor set for a baptism of fire amid a worsening cost-of-living crisis. Rowe, who joined M&S at the age of 15 before rising through the ranks, will end a 39-year career at the clothing and food group after presenting annual results on Wednesday that are expected to show a jump in profit. Along with chairman Archie Norman, Rowe has sought to transform the 138-year old M&S with a radical overhaul of its stor…