This patch fixes a correctness issue discovered in the int4 select(...) function on Apple Silicon machines, which causes bad bvh2 builds. Although the generated bvh2s give correct renders, the resulting runtime performance is terrible. This fix allows us to switch over to bvh2 on Apple Silicon giving a significant performance uplift for many of the standard benchmarking assets. It also fixes some unit test failures stemming from the use of MetalRT, and trivially enables the new pointcloud primitive.

Ref T92212