Function builtin_choose 

fn builtin_choose(
    args: &[RValue],
    _: &[(String, RValue)],
) -> Result<RValue, RError>

Binomial coefficient: choose(n, k) = n! / (k! * (n - k)!).

Uses the log-gamma formulation for numerical stability.

@param n numeric vector @param k numeric vector @return numeric vector of binomial coefficients