Cut out 2D Spectra

Cut out (possibly-overlapping) regions of an array corresponding to different 2D spectra. This should be already included in NDData but might need to wrap it for spectral features

Start by reading the NDData region-cutting behavior and the existing spectral features exposed by specreduce. Determine the inputs and outputs needed for cutting possibly overlapping regions corresponding to 2D spectra, then verify that the resulting wrapper handles those regions as intended.

Written by the indexing model from the issue text.