remove gcd impl from bevy_render

[atlv24]

Objective

• bevy_render (poorly) implements gcd (which should be in bevy_math but theres not enough justification to have it there either anyways cus its just one usage)

Solution

• hardcoded LUT replacement for the one usage

Testing

• verified the alternative implementation of 4/gcd(4,x) agreed with original for 0..200

[BenjaminBrienen]

Shouldn't this have a unit test for at least a few cases?

edit: I guess new() itself probably has a few tests already

[BenjaminBrienen]

assert_eq! could've been used, but it doesn't matter at all for this.

[atlv24]

assert_eq! cant be used, it doesnt work in const {} context

[atlv24]

i can add tests, most of the renderer doesnt have any

[atlv24]

actually adding tests would require implementing gcd again, and if i hardcode values then the tests would literally be testing to check if an array equals itself. not much point here i think

[atlv24]

just leaving this here in case anyone wants to slap it into rust playground just to satisfy the itch

fn main() {
    for i in 0..200 {
        let a = (4 / gcd(i, 4)) as u32;
        let b = [1, 4, 2, 4][i as usize & 3];
        assert_eq!(a, b);
    }
    println!("done");
}

fn gcd(mut a: u64, mut b: u64) -> u64 {
    while b != 0 {
        let t = b;
        b = a % b;
        a = t;
    }
    a
}