Smaller DX/Common defects, verified

[CanReader]

• Input-layout AddRef leak: src/Graphics/DirectX11/DirectX11Shader.cpp:112.
• D3D12 debug layer never enabled anywhere, while DX11 does enable its own (DirectX11Renderer.cpp:72)
  which is why DX12 state bugs like Wire shadow filter quality to the quality tiers #35/Point light shadows #36 went undetected. DX12 adapter selection is also dead code.
• Per-texture shader-visible descriptor heaps are created but never bound (DX12).
• Trailing pendingState dropped: src/Graphics/Common/RenderCommandQueue.cpp:176: the last queued
  state change never applies.
• DrawIndexedCommand applies startIndexLocation to the vertex buffer, while baseVertexLocation is
  dead.

Severity: minor individually; the missing DX12 debug layer is the reason the two corruption-class DX12
bugs above survived.

Found by a full audit of the graphics layer. Assessed severity: minor: cluster.