Fix: Closes shapes for 3d gizmos

[kfc35]

Objective

• Fixes Bevy 3d_gizmos doesn't have closed shapes #22204

Solution

• Refactored the solution from Make Gizmos::rect_2d and primitive_2d draw the joint of the first corner of closed shapes #22085 and made it use 3 dimensions; have 2d lineloop delegate to the 3d one.
• Updated any relevant usages of linestrip to use lineloop (rect and GizmoPrimitive3d<Triangle3d>). GizmoPrimitive3d<Polyline3d>, cube(), and aabb3d() still use linestrip. As far as I could tell, the cube looked ok for all corners in the 3d_gizmos example (the black cube in the center of the scene) but another pair of eyes could be helpful there.
• This does not do anything for Draw joints for closed shapes without redrawing the first line segment #22095 !

Testing

• Ran cargo run --example 3d_gizmos --features=free_camera and saw that the green 3d square gizmo now closes

• Ran the demo in Make Gizmos::rect_2d and primitive_2d draw the joint of the first corner of closed shapes #22085 and ensured no regressions for 2d_gizmos
• Ran a modified demo for Triangle3d and verified that Triangle3d now closes

Modified Demo for Triangle 3d

use bevy::prelude::*;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .add_systems(Update, draw_shapes)
        .run();
}

fn setup(
    mut config_store: ResMut<GizmoConfigStore>,
    mut commands: Commands
)
{
    let (config, _) = config_store.config_mut::<DefaultGizmoConfigGroup>();
    config.line.width = 10.0;
    config.line.joints = GizmoLineJoint::Miter;

    commands.spawn((Camera3d::default(), 
        Transform::from_xyz(0.0, 0.0, -5.0).looking_at(Vec3::ZERO, Vec3::Z)));
}

fn draw_shapes(mut gizmos: Gizmos) {
    gizmos.primitive_3d(
        &Triangle3d { vertices: [Vec3::ZERO, Vec3::new(1.0, 0., 0.), Vec3::new(0.0, 1.0, 0.) ] },
        Vec3::new(0.0, 0.0, 0.),
        Color::srgb_u8(0xFF, 0, 0)
    );
}

Before (notice notch in bottom left hand corner):

After (notch in bottom left hand corner is gone):