[FEATURE] Spatial Iterating

[AstroPatty]

Is your feature request related to a problem? Please describe.
OpenCosmo 0.9 introduces the ability to iterate over rows in a dataset or collection and perform complex computations over the value. In 0.10, we will introduce a spatial iterating tool that will allow users to map a computation over physical space.

Describe the solution you'd like
Allow users to specify the size of the sample regions and a sampling strategy (e.g. random or grid). The results can be collected into a data structure of the user's choosing, with the option to specify custom insert logic.

Use Case
Creating maps of quantities that are not present in the original catalogs.

Additional context
This may require some significant rework to the way MPI work is handled, as some samples will inevitably straddle the boundaries between ranks.