[idd] serialize monitor replugs with swap chain teardown

Keep the replug lifecycle gated until the old swap chain has drained and
released its pending frame, and the replacement swap chain is fully
initialized. Coalesce additional requests into a follow-up replug to
prevent overlapping topology changes and IddCx release-frame timeout
bugchecks.

idd/LGIdd/CIndirectMonitorContext.cpp

@@ -78,6 +78,7 @@ void CIndirectMonitorContext::AssignSwapChain(IDDCX_SWAPCHAIN swapChain, LUID re
     break;
   }
 
+  m_devContext->OnSwapChainAssigned();
   std::unique_ptr<CSwapChainProcessor> processor(new CSwapChainProcessor(
     m_monitor, m_devContext, swapChain, dx11Device, dx12Device, newFrameEvent));
 
@@ -103,7 +104,11 @@ void CIndirectMonitorContext::UnassignSwapChain()
   dx12Device = std::move(m_dx12Device);
   ReleaseSRWLockExclusive(&m_lock);
 
+  const bool hadSwapChain = !!processor;
   processor.reset();
   dx11Device.reset();
   dx12Device.reset();
-}
+
+  if (hadSwapChain)
+    m_devContext->OnSwapChainReleased();
+}