Add support for decals on `Cesium3DTileset`

[j9liu]

Feature

This should be fairly straightforward; we could expose a boolean option on Cesium3DTileset to enable decals. Then thread that through to the bReceiveDecals setting on our UStaticMeshComponents.

Example use case: https://community.cesium.com/t/how-to-show-car-movement-marks-footprints-on-cesium-3d-tileset-in-unreal/41966

[JH-KH-VDC]

Other use cases I could think of that I would use for Arch Viz type work:

• updating roadway markings and/or building textures
• blending/transitioning tileset data with user models
• animating textures on tileset with sequencer or in game/application through BPs