Unify handling of DRM devices between DRM and VAAPI

SDL may not be able to give us a DRM FD for Vulkan windows.

app/streaming/streamutils.h

@@ -36,4 +36,10 @@ public:
 
     static
     bool hasFastAes();
+
+    static
+    int getDrmFdForWindow(SDL_Window* window, bool* needsClose);
+
+    static
+    int getDrmFd(bool preferRenderNode);
 };