D3D validation error about resources being deleted while in use

We believe this is a bug in the D3D validation layer, rather than an actual error in our code. We're in touch with Microsoft about it, but I'll make this ticket to track the progress of that investigation.

Reported in [Link Removed], but also seen locally from time to time. Steps from the UDN:

I managed to get a reproduction by using the Matrix City Sample:

• Open the Editor passing -d3ddebug on the command line
• Once the level has loaded, fly around a little bit
• If it doesn't crash
  • Open the NaniteTools window -> Optimize
  • Set the threshold to 0
  • Untick the bottom 3 boxes
  • Press "Convert to Nanite"
  • Fly around again
• Eventually observe D3D validation error (and crash if it's not running under a debugger): Error: ID3D12Resource2::<final-release>: CORRUPTION: An ID3D12Resource object (0x000001BFE0B44F70:'Nanite.VisibleClustersSWHW') is referenced by GPU operations in-flight on Command Queue (0x000001BE8EAA69C0:'3D Queue 0'). It is not safe to final-release objects that may have GPU operations pending. This can result in application instability. (The name of the resource will be different on each run.)