feat(stdlib): Use lookup for integer parsing

[tibordp]

Quick microbenchmark

use std::time::Instant;

fn main() {
    let start = Instant::now();
    let sum = 0u64;
    const hexu64 = "ec19cb9f7768724f";
    for i in 0..1000000000 {
        sum += u64::parse_with_radix(hexu64, 16).unwrap();
    }
    println!("sum = {}", sum);
    println!("time = {}", Instant::now().duration_since(&start));
}

Before

sum = 11033462181226632704
time = 00:00:37.924432777

After

sum = 11033462181226632704
time = 00:00:13.741396338

That's quite incredible 🤣