Delete replay outputs on replay thread, not on UI thread

* On OpenGL this can cause problems with not being able to make the
  output context current because it's already current on the replay
  thread.

qrenderdoc/Windows/BufferViewer.cpp

@@ -1330,7 +1330,9 @@ void BufferViewer::stageRowMenu(MeshDataStage stage, QMenu *menu, const QPoint &
 BufferViewer::~BufferViewer()
 {
   if(m_Output)
-    m_Output->Shutdown();
+  {
+    m_Ctx.Replay().BlockInvoke([this](IReplayController *r) { m_Output->Shutdown(); });
+  }
 
   if(m_ModelVSIn->indices)
     m_ModelVSIn->indices->deref();

qrenderdoc/Windows/TextureViewer.cpp

@@ -659,7 +659,9 @@ TextureViewer::TextureViewer(ICaptureContext &ctx, QWidget *parent)
 TextureViewer::~TextureViewer()
 {
   if(m_Output)
-    m_Output->Shutdown();
+  {
+    m_Ctx.Replay().BlockInvoke([this](IReplayController *r) { m_Output->Shutdown(); });
+  }
 
   m_Ctx.BuiltinWindowClosed(this);
   m_Ctx.RemoveCaptureViewer(this);