Add filter function that subsets the entire object

[timtreis]

Users can easily break SpatialData objects by filtering the contained AnnData tables using scanpy - this might remove observations that are still present in other elements, such as Shapes. This function properly filters the entire object, enabled things such as shown here:

[LucaMarconato]

Hi thanks. Can you show an example of error that occurs after the legacy filtering? Such mismatch between tables and shapes are supported by design, so I think the broken behavior is a bug.