Support `spimdata` with a dedicated wrapping class.

[xulman]

The centerfold class is expected to provide its content in various types (while operating over the same memory to the greatest extent possible). Among the assumed exported types belonged also the SpimData. However, this is a type that's expected to become deprecated, soon or later.

So, we are about to remove it from the centerfold class and reintroduce it later in a separate, dedicated wrapping class (a conversion class) if needed.

👉 Let this issue serve as a memory of this plan ;-)

[stefanhahmann]

Use case: https://forum.image.sc/t/ome-zarr-and-the-spimdata-metadata-model-where-did-the-viewsetup-entity-layer-go/121958