Don't rely on getting WM_NULL messages in wxIdleWakeUpModule

Since the switch to using an event object for idle handling wakeup,
WM_NULLs are not being sent any longer, so wxIdleWakeUpModule didn't do
anything, resulting in pending event dispatching being paused while our
event loop was not running, as it happened, for example, while the
window was resized.

See #17579.

src/msw/evtloopconsole.cpp

@@ -71,6 +71,11 @@ void wxMSWEventLoopBase::WakeUp()
         wxLogLastError(wxS("SetEvent(wake)"));
 }
 
+bool wxMSWEventLoopBase::MSWIsWakeUpRequested()
+{
+    return ::WaitForSingleObject(m_heventWake, 0) == WAIT_OBJECT_0;
+}
+
 #if wxUSE_THREADS
 
 WXDWORD wxMSWEventLoopBase::MSWWaitForThread(WXHANDLE hThread)