Enhancement: Back up and restore SecurityDescriptors on Windows

Restic now backs up and restores SecurityDescriptors for files and folders on
Windows which includes owner, group, discretionary access control list (DACL)
and system access control list (SACL).

This requires the user to be a member of backup operators or the application
must be run as admin. If that is not the case, only the current user's owner,
group and DACL will be backed up, and during restore only the DACL of the
backed up file will be restored, with the current user's owner and group
being set on the restored file.

https://github.com/restic/restic/pull/4708
