Support quantized data in voxel code

3D Tiles 1.1 [property tables](https://github.com/CesiumGS/3d-tiles/tree/draft-1.1/specification/Metadata/ReferenceImplementation/PropertyTable), which are the basis of the new voxel format, have `offset` and `scale` fields which can used to transform quantized data (typically uint8 or uint16 values) into floating point values. The voxel code should be using these fields to transform property values in the shader.

Read the linked 3D Tiles 1.1 PropertyTable reference implementation, then locate the Cesium voxel code and its shader path. Trace how property values reach the shader and verify that the offset and scale fields transform quantized values into floating-point values.

Written by the indexing model from the issue text.