Fixed an issue where both `ARRaycastManager` and `ARPointCloudManager` could attempt to copy invalid `NativeArray`s when using the raycast fallback API.
Fixed issue 960 where `ARPointCloudManager.Append` could incorrectly throw an `ArgumentException`. For developers with custom implementations of `XRRaycastSubsystem.Provider` which do not support raycasting with an arbitrary ray, fallback raycasts including hits from point clouds will now correctly return all values.
Fixed issue 963 where `ARRaycastManager.RaycastFallback` would sometimes return incomplete results. Developers with custom implementations of `XRRaycastSubsystem.Provider` which do not support raycasting with an arbitrary ray will now see correct results from `ARRaycastManager.Raycast(Ray, TrackableType, Allocator)`.
