Fix wall segments for tiny extruded geometry

[hpinkos]

Replaces #8035

This if statement was incorrectly passing for the test case below, so I made it more robust. It should only continue if the adjacent positions are the same, meaning we are at a corner of the wall and shouldn't connect those vertices.

var viewer = new Cesium.Viewer('cesiumContainer', {
    imageryProvider : Cesium.createTileMapServiceImageryProvider({
        url : Cesium.buildModuleUrl('Assets/Textures/NaturalEarthII')
    })
});

var positions = Cesium.Cartesian3.fromDegreesArray([
    7.757161063097392, 48.568676799636634,
    7.753968290229146, 48.571796467099077,
    7.755340073906587, 48.571948854067948,
    7.756263393414589, 48.571947951609708,
    7.756894446412183, 48.569396703043992
]);

viewer.entities.add({
    polygon : {
        hierarchy : positions,
        extrudedHeight: 100.0,
        material : Cesium.Color.GREEN,
        outline : true,
        closeTop : false,
        closeBottom : false,
        arcType : Cesium.ArcType.RHUMB // causes missing volume
    }
});

function lookAt() {
    viewer.camera.lookAt(positions[1], new Cesium.Cartesian3(1000.0, 1000.0, 1000.0));
    viewer.camera.lookAtTransform(Cesium.Matrix4.IDENTITY);
}

Sandcastle.addToolbarButton('reset view', function() {
    lookAt();
});

lookAt();

[cesium-concierge]

Thanks for the pull request @hpinkos!

• ✔️ Signed CLA found.
• ❔ CHANGES.md was not updated.
  • If this change updates the public API in any way, please add a bullet point to CHANGES.md.
• ❔ Unit tests were not updated.
  • Make sure you've updated tests to reflect your changes, added tests for any new code, and ran the code coverage tool.

Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.
• Works (or fails gracefully) in IE11.

[hpinkos]

@likangning93 please review

[likangning93]

@hpinkos works as advertised 👍

Just seeing the issue in #8188, but that doesn't seem like a reason to hold this PR back.