tdf#97362: TextPortionEnumerationTest partially migrated to python (test_portion_enumeration_test.py)

Add footnote tests:
- test_refmark_point
- test_refmark
- test_toxmark_point
- test_toxmark
- test_hyperlink
- test_hyperlink_empty
- test_ruby
- test_ruby_empty

Change-Id: I0920517b5e8806a5fc46708822fed33006f03fd5
Reviewed-on: https://gerrit.libreoffice.org/38418Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>