Defer cursor winrt event triggering (#10685)

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## Summary of the Pull Request

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## References

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## PR Checklist
* [X] Supports #10563
* [ ] CLA signed. If not, go over [here](https://cla.opensource.microsoft.com/microsoft/Terminal) and sign the CLA
* [ ] Tests added/passed
* [ ] Documentation updated. If checked, please file a pull request on [our docs repo](https://github.com/MicrosoftDocs/terminal) and link it here: #xxx
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx

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## Detailed Description of the Pull Request / Additional comments

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## Validation Steps Performed

src/buffer/out/cursor.cpp

@@ -315,6 +315,11 @@ void Cursor::StartDeferDrawing() noexcept
     _fDeferCursorRedraw = true;
 }
 
+bool Cursor::IsDeferDrawing() noexcept
+{
+    return _fDeferCursorRedraw;
+}
+
 void Cursor::EndDeferDrawing() noexcept
 {
     if (_fHaveDeferredCursorRedraw)

src/buffer/out/cursor.h

@@ -55,6 +55,7 @@ public:
     const COLORREF GetColor() const noexcept;
 
     void StartDeferDrawing() noexcept;
+    bool IsDeferDrawing() noexcept;
     void EndDeferDrawing() noexcept;
 
     void SetHasMoved(const bool fHasMoved) noexcept;

src/cascadia/TerminalCore/Terminal.cpp

@@ -1070,7 +1070,12 @@ void Terminal::_AdjustCursorPosition(const COORD proposedPosition)
         _buffer->GetRenderTarget().TriggerScroll(&delta);
     }
 
-    _NotifyTerminalCursorPositionChanged();
+    // Firing the CursorPositionChanged event is very expensive so we try not to do that when
+    // the cursor does not need to be redrawn.
+    if (!cursor.IsDeferDrawing())
+    {
+        _NotifyTerminalCursorPositionChanged();
+    }
 }
 
 void Terminal::UserScrollViewport(const int viewTop)