retroarch: auto-detect joypads

Set the 'joypad_autoconfig_dir' setting to where autoconfig files are,
instead of using the built-in default of ~/.config/retroarch/autoconfig,
which is empty.

Tested with my PS5 DualSense controller, which now works.

pkgs/top-level/all-packages.nix

@@ -2651,6 +2651,9 @@ with pkgs;
       withAssets = true;
       withCoreInfo = true;
     };
+    settings = {
+      joypad_autoconfig_dir = "${retroarch-joypad-autoconfig}/share/libretro/autoconfig";
+    };
   };
 
   retroarch-assets = callPackage ../applications/emulators/retroarch/retroarch-assets.nix { };