Improvements to div_euclid and rem_euclid

[erg352]

What problem does this solve or what need does it fill?

• Currently, If we want to use div_euclid and rem_euclid conjointly on a type, we have to call both functions seperately. When looking at rust's standard library, there's a function specifically for this use case, making it more ergonomic and (maybe?) making certain optimisations possible.
• types like vectors have div_euclid and rem_euclid take as operand another vector of the same type. This means we often write code like: v.div_euclid(IVec3::splat(value)). This is a little convoluted, and makes it unclear whether or not the compiler will duplicate memory. On low optimization levels (opt-level=0, debug builds), splat does not seem to inline, and I could not verify on opt-level=3 whether data is duplicated, although it apeared not to.

Describe the solution you'd like

Define functions div_rem_euclid for common types.

Have these functions work like the standard library using a trait, that would allow for variable operands. For example:

pub trait Euclid<T> {
    fn div_euclid(&self, v: &T) -> Self;
    fn rem_euclid(&self, v: &T -> Self;
    fn div_rem_euclid(&self, v: &T) -> (Self, Self) {
        (self.div_euclid(v), self.rem_euclid(v))
    }
}

impl Euclid<IVec3> for IVec3 {
   ...
}

impl Euclid<i32> for IVec3 {
   ...
}

...

[bitshifter]

Note that the num crate and div_rem_euclid aren't part of the std library https://doc.rust-lang.org/std/index.html?search=div_rem_euclid, it looks like something that num has added. Perhaps there is a proposal to add it to std. Not that it makes much difference to the request.