XWIKI-22351: The autosave triggers a merge conflict sometimes even if there's...

XWIKI-22351: The autosave triggers a merge conflict sometimes even if there's no save done outside the realtime session
* Update tests (when inserting a block widget from an empty paragraph, at the end of the edited content, the widget is inserted before that paragraph; the paragraph was previously wrongly considered as block separator in wiki syntax; moreover, CKEditor output a non-breaking space in empty paragraphs).