TMDM-7848: "Integrated Matching won't work on entities having collections of Foreign Keys : merge will fail on empty collection"

Fix issue in partial update when new document has empty collection and collection is nested inside document (not last field).
Amend matching test to test this since integrated matching uses partial update to build golden record.
(https://jira.talendforge.org/browse/TMDM-7848)
Merge branch 'maintenance/5.6'