Add minimumPixelSize to ModelExperimental

[lilleyse]

Part of #9520 for bringing ModelExperimental to production.

Three properties from Model should be added to ModelExperimental:

• scale
• minimumPixelSize
• maximumScale

These control the scale of the computed model matrix. When either of these values is changed updateModelMatrix should be called. When minimumPixelSize does not equal zero, updateModelMatrix should always be called since the world space scale is constantly fluctuating to maintain a constant screen space scale.

The ModelExperimental implementation of these properties can be modeled after backFaceCulling. They should be added to the constructor, to fromGltf, and there should be getters and setters. updateModelMatrix in ModelExperimentalSceneGraph should compute the scale from these three properties and apply that to the model matrix. Generally the scale can be computed similar to getScale in Model except no need to handle the 2D specific code.