common/dir: Add reply_type parameter to system helper dbus calls
common/dir: Add reply_type parameter to system helper dbus calls

Make flatpak_dir_system_helper_call capable of dealing with a GUnixFDList
parameter and subsequently call g_dbus_connection_call_with_unix_fd_list_sync
for those methods.

Closes: #2657
Approved by: alexlarsson

matthiasclasen/flatpak,matthiasclasen/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,flatpak/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak,matthiasclasen/flatpak