fdo#75158 : Handled unsupported fields for docx file.

  - Handled unsupported fields using fieldmark API.
  - Added Unit Test.

Change-Id: I0c69458f330fa2e98821c392ea97410fe1b1e20e
Reviewed-on: https://gerrit.libreoffice.org/8391
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>