Fix polygons using rhumb lines across IDL

[shehzan10]

Polygons with rhumb lines weren't being correctly rendered across the IDL because of subdivision. This has now been fixed.

Doesn't affect Polylines, PolygonOutlineGeometry etc.

I added a spec for the IDL test case. The change in computation also required updating the existing spec for the function.

Sandcastle to test:

var viewer = new Cesium.Viewer('cesiumContainer');

var purplePolygonUsingRhumbLines = viewer.entities.add({
    name : 'Purple polygon using rhumb lines with outline',
    polygon : {
        hierarchy : Cesium.Cartesian3.fromDegreesArray([-170.0, 45.0,
                                                        170.0, 45.0,
                                                        170.0, 55.0,
                                                        -170.0, 55.0]),
        extrudedHeight: 50000,
        material : Cesium.Color.PURPLE,
        outline : true,
        outlineColor : Cesium.Color.MAGENTA,
        arcType : Cesium.ArcType.RHUMB
    }
});

var degrees = [
    170, 50,
   -170, 50,
   -170, 40,
    175, 40,
    175, 30,
   -170, 30,
   -170, 20,
    170, 20
];

viewer.entities.add({
    name : 'rhumb',
    polygon : {
        hierarchy : Cesium.Cartesian3.fromDegreesArray(degrees),
        arcType : Cesium.ArcType.RHUMB,
        material : Cesium.Color.BLUE.withAlpha(0.5),
        height: 0
    }
});

viewer.zoomTo(viewer.entities);

@likangning93 Can you review? Thanks for letting me know of this.

[cesium-concierge]

Thanks for the pull request @shehzan10!

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[likangning93]

Thanks @shehzan10!