Get the current WGI controller list at startup

On Win32 this list is empty and we always get controller added events. On UWP, this list is populated and we don't get controlle added events for currently connected controllers.

src/joystick/windows/SDL_windows_gaming_input.c

@@ -532,6 +532,24 @@ WGI_JoystickInit(void)
         if (!SUCCEEDED(hr)) {
             SDL_SetError("add_RawGameControllerRemoved() failed: 0x%lx\n", hr);
         }
+
+        __FIVectorView_1_Windows__CGaming__CInput__CRawGameController *controllers;
+        hr = __x_ABI_CWindows_CGaming_CInput_CIRawGameControllerStatics_get_RawGameControllers(wgi.statics, &controllers);
+        if (SUCCEEDED(hr)) {
+            unsigned i, count = 0;
+
+            hr = __FIVectorView_1_Windows__CGaming__CInput__CRawGameController_get_Size(controllers, &count);
+            if (SUCCEEDED(hr)) {
+                for (i = 0; i < count; ++i) {
+                    __x_ABI_CWindows_CGaming_CInput_CIRawGameController *e = NULL;
+
+                    hr = __FIVectorView_1_Windows__CGaming__CInput__CRawGameController_GetAt(controllers, i, &e);
+                    if (SUCCEEDED(hr) && e) {
+                        IEventHandler_CRawGameControllerVtbl_InvokeAdded(&controller_added, (IInspectable *)controllers, e);
+                    }
+                }
+            }
+        }
     }
 
     return 0;