Returns a Vec of the powers of a 2^nth primitive root of unity in some configuration
config. For example, in a Natural config this would yield: w^0, w^1, w^2…
Returns 2^order / 2 twiddle factors for FFT in some configuration config.
Twiddle factors are powers of a primitive root of unity of the field, used for FFT
computations. FFT only requires the first half of all the powers