Support glTF EXT_mesh_primitive_edge_visibility in iTwin.js

[markschlosseratbentley]

We should add support to iTwin.js for the proposed EXT_mesh_primitive_edge_visibility glTF extension. This will allow iTwin.js to support the latest upcoming glTF technology.

As we consider this work, we can consult #8312 on iTwin.js for some insight on how to support a new glTF extension. That PR was recently merged and supports another proposed glTF extension: EXT_mesh_primitive_restart.

[markschlosseratbentley]

@pmconne assigning you just because you have a PR up: #8366
Please feel free to un-assign if your priorities shift.