Function prime_tools::is_u64_prime

pub fn is_u64_prime(x: u64) -> bool

Figures out if a u64 is prime.

This is pretty slow: I've benchmarked it at 26 seconds to process only 200 random u64s. :(

Todo: use fermat's little theorem to make this faster.

assert_eq!(
    prime_tools::is_u64_prime(23_423_412_349),
    true
);

assert_eq!(
    prime_tools::is_u64_prime(23_423_414_138),
    false
);

assert_eq!(
    prime_tools::is_u64_prime(1),
    false
);