Feature request: lazy parsing of the pyramidal OME-TIFF morphology focus in Xenium

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Saving and reloading is the general recommendation for SpatialData objects coming from spatialdata-io. Nevertheless there is more to say here. In the case of Xenium >= 2.x.x and the morphology_focus image, we could actually take advantage of the pyramidal OME-TIFF format and construct the multiscale image directly from each scale and chunk (instead of lazily loading the large image and downscaling to a custom chunk size). This is currently not done as the spatialdata.models.Image2DModel.parse() method does not accept a DataTree object, but only a DataArray. If we extend this we can then also add this feature to spatialdata-io. Saving and reloading the object would still be preferable, but it would not be necessary for the case you reported.

Originally posted by @LucaMarconato in #1161

Start with spatialdata.models.Image2DModel.parse() and inspect how it currently handles DataArray inputs. Then trace the Xenium morphology_focus path in spatialdata-io and the pyramidal OME-TIFF loading entry point. Done means DataTree input is supported and morphology_focus can be constructed lazily from its scales and chunks without requiring save-and-reload.