NEW YORK — Cops who searched the backpack of accused Queens serial stabber Jermain Rigueur found a bloody hooded sweatshirt and six-inch, fixed-blade hunting knife, prosecutors said Friday. After Rigueur’s arrest following a two-day stabbing rampage that left a trail of victims across Jamaica and Springfield Gardens, police had to wait a day to search the gray Mancro backpack Rigueur was wearing when he was taken into custody. Inside cops found human blood inside the hood and sleeves of the dark gray sweatshirt and a menacing knife they believe Rigueur was wielding when he had a neighborhood o…