[BUGFIX] Opposite MM relation between both new entities not created

Scenario:
* usage in a workspace
* tt_content and sys_category records are created at the same time
  with defining an MM relation
* sys_category.items (group/db field, with MM and opposite usage
  defined) is filled with accordant tt_content record

Problem:
* the remap-stack in DataHandler does not consider references that
  are defined in a group/db field
* thus, these kind of relations are just not set, since the opposite
  reference uid cannot be resolved

Solution:
* process group/db relations with new record uids in remap-stack

Resolves: #77374
Releases: master, 7.6
Change-Id: If5e6589e2a0995dc4fce3ff49bd309f2fdb6eb24
Reviewed-on: https://review.typo3.org/49337
Reviewed-on: https://review.typo3.org/49352


Reviewed-by: Oliver Hader <oliver.hader@typo3.org>
Tested-by: Oliver Hader <oliver.hader@typo3.org>