How to reproduce:
1. Download "DXRMemoyLeak.zip" project
2. Set Graphics API to DirectX12
3. Enter the PlayMode -> select "DXRTest" GameObject
4. Open a memory profiler tool (E.g. GPU Z)
5. In Inspector Window select "Recreate All" -> look at the memory profiler tool "Memory used" line

Expected result: No memory leak when building RayTracingAccelerationStructure
Actual result: Memory leak when building RayTracingAccelerationStructure

Reproducible in: 2019.3.1f1, 2020.1.0a22
Could not test with - 2019.2.20f1 and earlier (no DXR)

Notes:
- The average leak is about 150 MB, by clicking "Recreate All" more times - this can build up to 3000 MB leaked memory
- If "Recreate Acceleration Structure" is clicked after "Recreate Mesh", it rebuilds RayTracingAccelerationStructure and leaks memory
- Whenever "Recreate Mesh" is clicked, it recreates the mesh without memory leak
- "Recreate All Same Mesh Ptr" recreates the mesh in the same pointer and builds RayTracingAccelerationStructure without memory leak