flatpak: 1.2.4 -> 1.4.2

* Regenerated all patches for 1.4.2 and resolved
  any conflicts.

* fix-test-paths.patch doesn't copy the whole locale archive
  because we have C.UTF8 now.

* nixos/flatpak creates a Flatpak system helper user
  Change introduced in 1.3.2.

Changes:
See https://github.com/flatpak/flatpak/releases/tag/1.3.1 through
1.4.2.

nixos/modules/services/desktops/flatpak.nix

@@ -38,5 +38,13 @@ in {
       "$HOME/.local/share/flatpak/exports"
       "/var/lib/flatpak/exports"
     ];
+
+    users.users.flatpak = {
+      description = "Flatpak system helper";
+      group = "flatpak";
+      isSystemUser = true;
+    };
+
+    users.groups.flatpak = { };
   };
 }