Fix shadow flickering and shimmering with DLSS SR in DLSS NR

[cmh1448]

Summary

Fix shadow flickering and shimmering in DLSS Neural Rendering when the game uses DLSS Super Resolution instead of DLAA.

Problem

The DLSS NR integration assumed that motion vectors always used the guide/render resolution and started at (0, 0).

This assumption generally went unnoticed with DLAA, where the render and output resolutions match. With DLSS SR, however, motion vectors may be provided at either render or output resolution. Passing incorrect motion vector dimensions, subrects, or scaling metadata to DLSS NR caused unstable temporal reprojection, resulting in visible shadow flickering and shimmering.

Changes

• Respect the MVLowRes feature flag when determining motion vector dimensions
• Use the correct render- or output-resolution motion vector region
• Forward depth and motion vector subrect offsets supplied by the game
• Clamp subrect dimensions and offsets to the allocated resource bounds
• Scale horizontal and vertical motion vectors independently
• Apply the fix to both D3D12 and Vulkan paths
• Update the DLSS NR forwarder interfaces to pass the required metadata

Result

DLSS NR now receives motion vector metadata that matches the game's actual resources and DLSS mode, fixing the shadow flickering and shimmering observed with DLSS Super Resolution while preserving DLAA behavior.

Testing

• DLSS SR with D3D12
• DLAA with D3D12
• DLSS SR with Vulkan
• DLAA with Vulkan
• Release x64 build