[Ref] Import use process for relationship defaults, add test

[eileenmcnaughton]

Overview

Further code cleanup to use the processor class. In the process I discovered contact subtype is not yet set on the processor class - merging this in the same civi version as related cleanups would be safer.

Adds unit tests to cover

Before

Hard to read

After

Easier to read

Technical Details

Part of cleanup & adding unit tests

Comments

@colemanw @seamuslee001 I think we should merge this before 5.18rc is cut. Risk of edge case bug from not having set contactSubType is low but avoidable

[civibot]

(Standard links)

• If this is your first pull-request for CiviCRM, please browse CONTRIBUTING.md for information about the development and testing processes.
• If you are reviewing this pull-request, you may wish to consult the test sites and the Review Standards (long template, short template).

[seamuslee001]

seems to make sense to me adding merge on pass

[eileenmcnaughton]

uunrelated fail