We previously thought this wasn't possible because constant buffer offsets and
partial updates were unavailable, but we were reading the wrong table - this is
only the case for D3D11...
https://learn.microsoft.com/en-us/windows/win32/direct3d11/overviews-direct3d-11-devices-downlevel-intro
... while 12 doesn't list this feature at all:
https://learn.microsoft.com/en-us/windows/win32/direct3d12/hardware-feature-levels
We double checked and Jesse Natalie confirmed that this feature is required for
D3D12 even for 11_0 drivers. (Thanks Jesse!)
Additionally, D3D12 requires that UAVs are accessible from all shader stages,
meaning Tier 2 is enough to support the number of UAVs we need. Tier 1 could be
a property to lower the requirements, but that can be done later.
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