Fix D3D12 pixel history on MSAA depth stencils.

* Performing pixel history on an MSAA depth target caused a memory
stomp due to the depth and stencil copies being mis-identified as a
4-component operation, stomping the following 12 bytes. For the depth,
this stomped the stencil and the following padding, but when the
missing stencil copy was added in 4815ada it stomped
dsWithoutShaderDiscard as well. This triggered an assert due to a clear
event appearing to have frags associated with it.

renderdoc/driver/d3d12/d3d12_pixelhistory.cpp

@@ -1087,6 +1087,7 @@ private:
                                            ? D3D12_RESOURCE_STATE_DEPTH_READ
                                            : D3D12_RESOURCE_STATE_DEPTH_WRITE;
       targetCopyParams.srcImageFormat = GetDepthSRVFormat(m_CallbackInfo.targetDesc.Format, 0);
+      targetCopyParams.depthcopy = true;
       targetCopyParams.copyFormat = DXGI_FORMAT_R32_TYPELESS;
       offset += offsetof(struct D3D12PixelHistoryValue, depth);
     }