Add layers to Netcdf file using subgroups

[felixcremer]

We could add overviews to a NetCDF dataset in a similar way to how we work with zarr data. Using subgroups in the original dataset we could add the different layers with coarser resolutions and then implement a smart way to retrieve them from the NetCDF file.
I am not sure, how easy it would be to ignore these layers if we would open the data with different tools.
I am most likely not going to work on that in the near future.

This is an idea by @AlexanderBarth that came up during JuliaEO 2025.