Only use a transparent cursor on Windows when connected via RDP

VMware relies on the cursor being set to NULL to optimize relative mouse motion for games.

We should also revisit whether current RDP works better with a NULL cursor or a transparent cursor.

Fixes https://github.com/libsdl-org/SDL/issues/13700

(cherry picked from commit dac6af4ba6815fd88364820c48f55c878575d5bf)
(cherry picked from commit 55b599d69349e1ce7bf05694629f67ba8e00ba5e)

src/video/windows/SDL_windowsmouse.c

@@ -250,7 +250,10 @@ static void WIN_FreeCursor(SDL_Cursor *cursor)
 static int WIN_ShowCursor(SDL_Cursor *cursor)
 {
     if (!cursor) {
-        cursor = SDL_blank_cursor;
+        if (GetSystemMetrics(SM_REMOTESESSION)) {
+            // Use a blank cursor so we continue to get relative motion over RDP
+            cursor = SDL_blank_cursor;
+        }
     }
     if (cursor) {
         SDL_cursor = (HCURSOR)cursor->driverdata;