TMDM-7805: "result of explaining how existing group was matched by restapi is incorrect"

Fixes incorrect logic for comparing between merged values and new values (wasn't comparing all combinations between the 2 value sets leading to match=false results, especially when golden record was built using Concatenate survivorship).
Adds unit test for ensuring no regression on this.
(https://jira.talendforge.org/browse/TMDM-7805)