fdo#74325: Write unit test for cell note export to ods.

Change-Id: Ic145781a6c2d7fefb4e80b3a84735e0fb505b0e7
fdo#74325: Ensure that all note objects have an sdr object before exporting.

Otherwise, if a note hasn't been displayed at least once before saving
that note would not get saved.  In the future, we should modify the export
code to not rely on SdrObject to check the presence of note.

Change-Id: Ib7ca3ac00a0c9cdd3a01facda7af479ef172afbe