They’re taking out the trash at a glacial pace. An 8-foot-high mountain of trash near Gracie Mansion finally got cleared Monday after The Post revealed neighbors’ anger that Mayor Zohran Mamdani’s home apparently got the white-glove treatment — but other unsightly snowy garbage piles still linger across the city. The growing summits of hardened snow, plastic trash bags and other detritus remained more than a week after Winter Storm Fern blanketed the Big Apple with a foot of flakes that quickly