* Moves 3D Camera interpolation scene side.
* Automatically switches `get_camera_transform()` to report interpolated transform during `_process()`.
* Fixes `ClippedCamera` to work with physics interpolation.
Adds optional hierarchical culling to the 2D rendering (within VisualServer).
Each canvas item maintains a bound in local space of the item itself and all child / grandchild items. This allows branches to be culled at once when they don't intersect a viewport.