By Marlene Kennedy/For The Leader-Herald DOWN TO BUSINESS — Toy icon Barbie, who since her debut in 1959 has worked as a fashion model, chef, farmer, teacher, veterinarian, and on and on and on, has an immediate new career challenge: reviving Mattel’s doll line. Make no mistake that Mattel is doing fine. The company, which identifies Barbie, Hot Wheels and Fisher-Price as its toy “power brands,” raked in $5.4 billion in sales last year, on par with 2021 and up 20% from pre-pandemic 2019. But in the first quarter this year, Barbie got a call-out for the dip in sales…