Add support for I3S Building Scene Layer

Following on from the existing work for CesiumJS and integration of i3s scene layers as per this reference:

We would love to see added support for I3S Building Scene Layer in CesiumJS similar to 3D Object and Integrated Mesh Layers support.

Delivering this integration would unlock a treasure trove of 3D data into CesiumJS based applications in the BIM (Building Information Modelling) space.

The I3S BSL has been an OGC standard as part of OGC I3S 1.3 since late 22.

Here are some additional references with work that has occurred to date in this space:

Esri Blog

Cesium Blog