TMDM-7626 : "Error while saving composite keys staging record"

Fix copy() issue for entity types (copy loosing key field declaration original order).
Adds unit test for issue.
(https://jira.talendforge.org/browse/TMDM-7626)
Merge remote-tracking branch 'origin/maintenance/5.6' into feature/SCM-239/mavenstudiobuild
update some pom.xml and manifest to merge maint/5.6 into feature branch