This adds the selectbox to (hopefully) all filepickers:
- LO native
- GTK/GTK3
- KDE4
- KDE5
- Windows
- macOS

Change-Id: I01bd42b1ca18e0f691b879647a6cb1b62177d3ce
Reviewed-on: https://gerrit.libreoffice.org/49311Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>