Publicizing StereoKitTransforms properties

[austinbhale]

Hi! In the newest \psi release, there was the inclusion of the SpatialTransformsUpdater stepper: https://github.com/microsoft/psi/blob/39615ade7dca194770cc645c5c46a2da97000ceb/Sources/MixedReality/Microsoft.Psi.MixedReality.UniversalWindows/MixedReality.cs#L159

The expectations for this stepper are to (1) retrieve the latest world anchor for \psi rendering. (2) If the spatial anchor cannot be found when tracking is lost, then the value is set to null. (3) The renderers will not display anything when the spatial anchor is not found according to: https://github.com/microsoft/psi/blob/39615ade7dca194770cc645c5c46a2da97000ceb/Sources/MixedReality/Microsoft.Psi.MixedReality/StereoKit/Renderers/StereoKitRenderer.cs#L27

Now that the WorldHierarchy is considered dynamic with this newest stepper, could we have public access to StereoKitToWorld? Otherwise, in our application, we'd have to invert this matrix anytime we want to use it, which seems undesired: https://github.com/microsoft/psi/blob/39615ade7dca194770cc645c5c46a2da97000ceb/Sources/MixedReality/Microsoft.Psi.MixedReality.UniversalWindows/MixedReality.cs#L193

Similar issue to #259. This may be different as it is now a dynamic property.

[austinbhale]

We decided it might be better to stay in SK world, so this is not applicable to us. Not sure if this is useful for others, so closing this as not planned.

Thanks for the newest updates for MixedReality devices!