tdf#150927: properly handle nesting in tables
This re-implements the relevant part of commit
35021cd56b3b4e38035804087f215c80085564be, to follow the same
recursion logic that is used in SwXMLExport::ExportTable.
Additionally, it found a place where XML was still emitted
when collecting autostyles (breaks were exported); fixed.
Change-Id: I3b7eed06e0eca9ad20304b45db4c3e9d72478c9b
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/139901
Tested-by: Jenkins
Reviewed-by: Mike Kaganski <mike.kaganski@collabora.com>