Originally SpectrumViewerWindowModel had the dictionary mapping names to ROIs for the spectrum window. This allows things like get_spectrum() to be passed a name. SpectrumWidget also has a dict of ROIs, which is probably more essential.

This requires code to keep them in sync, and has been a source of issues.

get_spectrum() needed to be updated to be able to receive a SensibleROI for the RITS export, so its less important that the model knows about the names. Maybe it is possible to remove _roi_ranges completely.

Step 1:
In SpectrumViewerWindowModel.get_spectrum() remove the option to call with a str as the name. Update all callers.

Find all other cases where model uses its own list of ROIs. Pass them as arguments instead.

Step N:
Remove set_new_roi, set_roi, get_roi, rename_roi, remove_roi, get_list_of_roi_names from the model.