Respect OS language at NativeDesktop#getDefaultFileChooserDirectory

[koppor]

Fixes #8010 - especially #8010 (comment)

In Germany, the default "documents" folder is ~/Dokumente. Either we mirror all translations in JabRef - or we use FileSystemView.getFileSystemView().getDefaultDirectory().getPath(). (Source: https://stackoverflow.com/a/32914568/873282)

This partially reverts #9222.

### Compulsory checks
- [ ] Change in `CHANGELOG.md` described in a way that is understandable for the average user (if applicable)
- [ ] Tests created for changes (if applicable)
- [ ] Manually tested changed features in running JabRef (always required)
- [ ] Screenshots added in PR description (for UI changes)
- [ ] [Checked developer's documentation](https://devdocs.jabref.org/): Is the information available and up to date? If not, I outlined it in this pull request.
- [ ] [Checked documentation](https://docs.jabref.org/): Is the information available and up to date? If not, I created an issue at <https://github.com/JabRef/user-documentation/issues> or, even better, I submitted a pull request to the documentation repository.

[calixtus]

https://github.com/omajid/xdg-java/blob/master/src/main/java/org/freedesktop/BaseDirectory.java ?

[koppor]

omajid/xdg-java@master/src/main/java/org/freedesktop/BaseDirectory.java ?

Not sure what you mean by that. The environment variable XDG_DOCUMENTS_DIR seems to be unset at @dermalikmann s machine - see #8010 (comment) and the code

[calixtus]

I will test this on my machine, I noticed that the issue occurs on an Arch Linux distribution like mine either with gnome or KDE. I'm not yet convinced that not having the xdg vars set is an issue of the distribution.