Make `CesiumGlobeAnchor` use transform relative to `CesiumGeoreference`, rather than its parent

[j9liu]

Feature

Currently, CesiumGlobeAnchor's code operates on relative transforms. In situations where a globe-anchored object is parented or re-parented at runtime, even though its world position doesn't change, the relative transform results in an unexpected recomputation of Latitude/Longitude fields.

In most cases, an object is directly parented under a CesiumGeoreference, so using a relative transform makes sense. But this can be a bit restrictive for level setup, so a world-based option would be nice.

[j9liu]

To illustrate what I mean, here's what happens when I parent a globe-anchored sphere to a non globe-anchored cube:

The sphere is offset along the Z-axis from the cube, but otherwise has the same position. When the cube's at (0, 0, 0), the globe anchor's lat/lon should be equivalent to the CesiumGeoreference.

However, when you move the cube, the lat/lon of the globe anchor doesn't change, because the sphere's relative transform remains the same. You only see the change take effect once you reparent the sphere to the CesiumGeoreference, thus modifying the relative transform.