Provide helpful validation report for delete and archiving

Problem/Motivation

ILLUSTRATION OF SCENARIO A part i)

Scenario A)
ILLUSTRATION OF SCENARIO A part ii)

Previously we were lacking reporting of active references of archived moderation state candidate node in other published nodes.

Now have provided that (see commits)

ILLUSTRATION OF SCENARIO B

Scenario B)
Previously we were lacking reporting active references of delete candidate node in other nodes. (see illustration of scenario B ^.

Steps to reproduce

Scenario A)
i) add a linkit reference to node 123 in another published node.
ii) Now edit node 123 and set it's moderation state to 'archived'

Scenario B)
i) Add a linkit reference in a published or archived moderation state node.
ii) delete the node that is referenced.

Expected result: safe delete validation includes report of expected summary of references.

Proposed resolution

See commit

Remaining tasks

Make it so, then release

User interface changes

Yes, see screenshot

API changes

externally no, internally yes.

Data model changes