FZ: warn w/ a toast if an elevated window cannot be dragged and offer learning more

src/common/window_helpers.h

@@ -1,4 +1,7 @@
 #pragma once
 #include "common.h"
 
-HWND CreateMsgWindow(_In_ HINSTANCE hInst, _In_ WNDPROC pfnWndProc, _In_ void* p);
+HWND CreateMsgWindow(_In_ HINSTANCE hInst, _In_ WNDPROC pfnWndProc, _In_ void* p);
+
+// If HWND is already dead, we assume it wasn't elevated
+bool IsProcessOfWindowElevated(HWND window);