Add swizzle variants of with_X methods

[tim-blackbird]

• Implement the idea from Mutable Swizzles #516 (comment)

Example

Vec3::Y.with_xz(Vec2::ONE) // == Vec3::ONE

Notes

• Do we want set_X swizzles also?

• One complication is it would be good to support Vec3 and Vec3A as the thing vector which will probably make the trait slightly more complex.

  Quote from the linked comment. Trivial to solve by taking impl Into<{{ vec3_t }}> though that would allow [f32, f32, f32], etc. as well.

[bitshifter]

Ah right, I guess I didn't see a need to port the swizzle test generation to tera when I migrated everything else. This is the old swizzlegen code before it was deleted https://github.com/bitshifter/glam-rs/blob/88e4538695cf1babddec1a9778510790cd1d7671/swizzlegen/src/main.rs

[bitshifter]

Rather than adding it to tera I've restore enough of the old code to generate swizzle tests.

[bitshifter]

https://github.com/bitshifter/glam-rs/tree/main/swizzlegen

[tim-blackbird]

The tests use the values 11, 12 and 13 for the right hand side X, Y and Z components respectively.
This hopefully makes verifying correctness easy enough :)

// Examples
assert_eq!(v.with_xyz(rhs3), vec4(11_f32, 12_f32, 13_f32, 4_f32));

assert_eq!(v.with_zx(rhs2), vec4(12_f32, 2_f32, 11_f32, 4_f32));

[bitshifter]

I haven't reviewed every generated line but hopefully I've looked at enough to check things look correct AFAICT.

It took a little while to understand exactly what this does (having not used this in shaders) but it looks like it matches the https://registry.khronos.org/OpenGL/specs/gl/GLSLangSpec.4.60.pdf swizzle assignments.

The testing approach makes sense to me.

For set, it can be added later if there is a desire for it.

I think into Into<{{ vec3_t }}> would be more permissive than I would like. It could also be done by splitting the swizzle trait up https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=fbc9b6031e9224e27c286d256101d412, but I'll leave that for now, it complicates things and the benefits would be very niche.

Thanks for this, it's a pretty fiddly thing to implement.