Extendable gizmos primitives 3d

[lynn-lumen]

Objective

• Partially fixes GizmoPrimitiveNd for external primitives #13615

Solution

• GizmoPrimitive3d is now implemented for the primitive itself, allowing external primitives to also implement it.
  • Gizmos for 3d-primitives are now implemented in GizmoPrimitive3d::gizmos(&self, &mut gizmos, isometry, color) which may be called on the primitive itself. i.e.

    Sphere::new(1.0).gizmos(&mut gizmos, Isometry3d::IDENTITY, RED)

    is now valid.
• GizmoBuffer now implements a function primitive_3d<P: GizmoPrimitive3d > which can be used just like before.

Caveats

• There is a lot of weird lifetime stuff going on.
• You can call .gizmos(...) on primitives, which seems weird
• If accepted, this needs to be repeated for 2d primitives.

Testing

• Running the 3d_gizmos example

Migration Guide

• For most use cases, this should not require migration, besides removing unused imports.
  • If you did implement GizmoPrimitive3d for a custom GizmoBuffer-like struct, you will need to move your implementation for custom primitives to the primitive itself and use that implementation in a seperate method on the previously mentioned struct.

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