MapBox Vector Tile Support

Add support for MapBox Vector Tiles in cesium-native, including the core native parsing, streaming, and integration work needed to make vector tile data usable across Cesium’s native runtimes. This epic would track exploration and implementation of shared cesium-native capabilities that could potentially enable MapBox Vector Tile support in both Unreal and Unity, along with any platform-specific follow-on work needed to expose and render that data effectively.

No files, tests, or entry points are named. Start by surveying the existing cesium-native tile and runtime integration areas, then clarify the shared versus Unreal and Unity scope. Done would require native MapBox Vector Tile parsing, streaming, and integration, with any agreed platform-specific exposure and rendering work.

Written by the indexing model from the issue text.