Implement Meshable for some 3D primitives

[Jondolf]

Objective

Split up from #11007, fixing most of the remaining work for #10569.

Implement Meshable for Cuboid, Sphere, Cylinder, Capsule, Torus, and Plane3d. This covers all shapes that Bevy has mesh structs for in bevy_render::mesh::shapes.

Cone and ConicalFrustum are new shapes, so I can add them in a follow-up, or I could just add them here directly if that's preferrable.

Solution

Implement Meshable for Cuboid, Sphere, Cylinder, Capsule, Torus, and Plane3d.

The logic is mostly just a copy of the the existing bevy_render shapes, but Plane3d has a configurable surface normal that affects the orientation. Some property names have also been changed to be more consistent.

The default values differ from the old shapes to make them a bit more logical:

• Spheres now have a radius of 0.5 instead of 1.0. The default capsule is equivalent to the default cylinder with the sphere's halves glued on.
• The inner and outer radius of the torus are now 0.5 and 1.0 instead of 0.5 and 1.5 (i.e. the new minor and major radii are 0.25 and 0.75). It's double the width of the default cuboid, half of its height, and the default sphere matches the size of the hole.
• Cuboid is 1x1x1 by default unlike the dreaded Box which is 2x1x1.

Before, with "old" shapes:

Now, with primitive meshing:

I only changed the 3d_shapes example to use primitives for now. I can change them all in this PR or a follow-up though, whichever way is preferrable.

Sphere API

Spheres have had separate Icosphere and UVSphere structs, but with primitives we only have one Sphere.

We need to handle this with builders:

// Existing structs
let ico = Mesh::try_from(Icophere::default()).unwrap();
let uv = Mesh::from(UVSphere::default());

// Primitives
let ico = Sphere::default().mesh().ico(5).unwrap();
let uv = Sphere::default().mesh().uv(32, 18);

We could add methods on Sphere directly to skip calling .mesh().

I also added a SphereKind enum that can be used with the kind method:

let ico = Sphere::default()
    .mesh()
    .kind(SphereKind::Ico { subdivisions: 8 })
    .build();

The default mesh for a Sphere is an icosphere with 5 subdivisions (like the default Icosphere).

---

Changelog

• Implement Meshable and Default for Cuboid, Sphere, Cylinder, Capsule, Torus, and Plane3d
• Use primitives in 3d_shapes example

[NthTensor]

Some thoughts:

• I like that the default primitives are more uniformly scaled. Getting any more specific than that would be super bikeshedy.
• I like the api in general. Good use of the builder pattern.
• I would prefer if cuboid, plane, cylinder and torus got their own modules instead of living in dim3.

Looks pretty good all in all.

[spectria-limina]

I did a review ass, the biggest thing is I don't understand why you're duplicating all this code instead of making use of existing code where it exists. Duplicated code is fragile; it would be much more preferable to build a render::mesh::shape and convert that to a mesh where possible.

[NthTensor]

The plan is to remove the render shapes in a follow up. We are temporally copying rather than replacing to make the patch smaller and more manageable.

[alice-i-cecile]

I'm content with this, but I'd like to remove the duplicated code ASAP.