Unpacks a bigint back into a point on the Baby Jubjub elliptic curve, reversing the packing process.
This involves interpreting the bigint as the y-coordinate and extracting the sign of the x-coordinate
from the encoded format. The function then calculates the x-coordinate using the curve equation.
Unpacks a bigint back into a point on the Baby Jubjub elliptic curve, reversing the packing process. This involves interpreting the bigint as the y-coordinate and extracting the sign of the x-coordinate from the encoded format. The function then calculates the x-coordinate using the curve equation.