Make UVSphere 3d shape use Y-up convention

[coreh]

Objective

Before

After

• As noted by 0xC0DEDBAD on this Discord message our current UV Sphere is Z-up (with the poles on +Z, -Z). This PR makes it Y-up, to be more consistent with other 3d shapes.

Solution

• Swapped y and z in the math and also swapped first and second triangle indexes to preserve right-handedness;
• Flipped UV's V component.

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Changelog

Changed

• Made UVSphere Y-up (instead of Z-up) for consistency with other 3d shapes and Bevy's convention;

Migration Guide

• UVSphere poles are now on +Y, -Y. If you're currently relying on UVSphere poles being +Z, -Z, (e.g. for texturing/uv mapping purposes) you must rotate your UVSphere by PI / 2.0 (90º) on the X axis;

[coreh]

Hmm looking at it again, I'm still not 100% confident the UV's are correct, let me double check it before we merge this.

[alice-i-cecile]

On board with this: has my approval pending verification.