fix(file): add fallback for moving directories across filesystems

This could happen if a folder is mounted to another drive. The media folder is a good example for this.

The problem also occurs in plain Docker containers. The docker magic seems to create different filesystems.

This is a known problem (& solution), see:

• https://github.com/nextcloud/server/pull/38623
• https://bugs.php.net/bug.php?id=54097