PARIS — Seán McGirr’s debut show at Alexander McQueen, one of the season’s most anticipated shows, was inevitably one of its most controversial, because Lee McQueen himself was the biggest most of all: the most significant designer of modern times. Since his death in 2010, his legacy has been nurtured and enhanced by his right hand Sarah Burton who has made the brand a byword for exquisite craft. As the first “outsider” to be…