TMDM-6868: "Error when save values for nested multi-occurence element"

Fixes incorrect behavior when deleted contained field also contains fields to be deleted: required two passes to delete /a/b/c & a/b/d (one for a/b/c and one a/b/d).
Fixes incorrect clean up in DataRecord-based document (consider cleanup of contained empty DataRecord instances).
(https://jira.talendforge.org/browse/TMDM-6868)