Function mantissa_to_quantity 

pub fn mantissa_to_quantity(
    mantissa: i64,
    exponent: i8,
    precision: u8,
) -> Quantity

Converts a mantissa/exponent pair to a Nautilus [Quantity].

Uses pure integer arithmetic: raw = mantissa * 10^(FIXED_PRECISION + exponent).

Panics

Panics if mantissa is negative.