Make CartesianX.packArray() compatible with typed arrays

[ptrgags]

This fixes a bug where CartesianX.packArray() cannot be used on a typed array because it attempts to set array.length. This property is read-only for typed arrays like Float64Array

This PR fixes this for all three types of Cartesian vectors. It also updates the packing unit tests to make sure all three classes have the same set of packing tests.

Sandcastle example (Cartesian3 only)

[cesium-concierge]

Thanks for the pull request @ptrgags!

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Reviewers, don't forget to make sure that:

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

[hpinkos]

Thanks @ptrgags !