Stripping Level "Medium" breaks CesiumGeoJsonDocumentRasterOverlay

### What happened?

Hi fellow Cesium Users and Devs.

I want to share an observation:

When creating a build using the newest Cesium for Unity Plugin and programmatically creating a `CesiumGeoJsonDocumentRasterOverlay` using `FromDocument` as source, the functionally of `CesiumGeoJsonDocumentRasterOverlay` is stripped from the build (tested with WebGL) as long as the Managed Stripping Level is set to **Medium** or higher.

A easy workaround is setting the stripping level to "Low" or lower.

### Environment

Cesium for Unity version: 1.23.2
Unity Editor Version: 6000.3.10f1
Operating System: Win11 64Bit

### Reproduction steps

1. Under Project Settings > Player > Managed Stripping Level select a Setting higher than low.
2. Build

### Supporting evidence

_No response_