Refactor ArchesFileReader.import_business_data() for readability

[jacobtylerwalls]

At its maximum, there are 21 levels of indentation in this function. We should refactor to avoid so much indentation.

(The github preview below doesn't do it justice, so click through):

arches/arches/app/utils/data_management/resources/formats/archesfile.py

Lines 460 to 466 in c6b043a

	if (
	child_tile_cardinality
	== "1"
	):
	populated_child_nodegroups.append(
	prototype_tile.nodegroup_id
	)

[chiatt]

It would be nice to transition away from this and the csvfile importer and use the bulk data manager for these formats instead.