[Feature Request] Add function to compute chunksize on disk

[felixcremer]

As discussed at todays workshop, it would be good to have a function to compute the size of the chunks on disk.
This should either take a diskarray to get the current chunksizes on disk or to get the estimated sizes from a Tuple of possible chunk sizes and an element type.

[meggart]

Which chunk size exactly do you need exposed and what would be the main use case? Size of uncompressed chunks would be very easy to do, as you write it can be computed from chunk sizes and element type. Compressed chunk sizes would be very tough and need a new interface function that must be implemented by the respective backends.