Fix for AxisAlignedBoundingBox clone method

[hanbollar]

before the fix - if result was not defined returned constructed AxisAlignedBoundingBox without copying over center value.

The issue with this is that if the user, for their own purposes, constructed a center value with an offset s.t. the minimum and maximum weren't the same distance away from the center parameter, the clone method would not consider this form of construction and just solve for the default center based on max and min values.

Additionally, since the minimum and maximum values are defined in relation to the center (ie as if the center was the origin for them) the clone's box's overall position doesnt match that of the box it's cloning.

[cesium-concierge]

@hanbollar, thanks for the pull request! Maintainers, we have a signed CLA from @hanbollar, so you can review this at any time.

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[hpinkos]

Good catch @hanbollar!

I think we prefer this fix though

if (!defined(result)) {
    return new AxisAlignedBoundingBox(box.minimum, box.maximum, box.center);
}

[hpinkos]

Also, please add a unit test

[hanbollar]

@hpinkos updated with your recommendations - lmk if there's anything else you think I should do before it can merge. Thanks!

[hpinkos]

Perfect, thanks @hanbollar!