2.5D visualization #330

Currently the SpatialData 3d models are not supported for visualization in napari-spatialdata. While there is a large change for performance issue when visualizing 3D rendering, 2.5D rendering should be ok. The main thing that needs to happen is adding the support for the 3D SpatialData models. Next, for shapes / points if the z coordinates are continuous then we need to be able to bin the coordinates on the fly so we can visualize in 2.5D. Similar to scverse/spatialdata-plot#386.