Officially deprecate stageObject() and loadObject() in favor of saveObject() and readObject(), respectively.
The former have been soft-deprecated and scrubbed from documentation for quite some time, so it is unlikely that anyone is using them.
We also deprecated related functions like stageSpatialImage() and loadSpatialImage().
Dispatch to saveObject() for any of the SpatialExperiment's images that implement a dedicated method for it.