Add Draco quantization workaround for point clouds

[ebogo1]

This fixes a regression from 1.86 after updating Draco, where SkipAttributeTransform broke future attribute lookups with GetAttributeByUniqueId. To reproduce, see this Sandcastle and select the "PointCloudDraco" tileset.

This change is analogous to #9904, but since decodePointCloud always tries to call SkipAttributeTransform on "POSITION" and "NORMAL", those are the two attributes that use GetAttributeId and GetAttribute instead of GetAttributeByUniqueId.

[cesium-concierge]

Thanks for the pull request @ebogo1!

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Reviewers, don't forget to make sure that:

• Cesium Viewer works.
• Works in 2D/CV.

[lilleyse]

@ebogo1 looks good. At one point you mentioned that there was a point cloud draco test that had been removed in #9841 that was still failing. Is that still the case, or can we add it back now?

[ebogo1]

@lilleyse Good catch - I added the tests back in 6c55ad1.