Feature: temporal MetalFX upscaling at present for games with motion vectors

[dracinn]

Request

Present-time upscaling through MetalFX's temporal scaler (MTL4FXTemporalScaler) where the game supplies motion vectors — an upgrade from today's spatial-only DM_PRESENT_UPSCALE=metalfx.

Rationale

DM_PRESENT_UPSCALE uses MTL4FXSpatialScaler, which is a single-frame upscale. The host already builds a MTL4FXTemporalScaler for the NVN2 DLSS path with the game's real depth and motion vectors — the same inputs a temporal present-scale would need. For games that hand the host MVs (DLSS path), a temporal scaler at present would give markedly better reconstruction quality than spatial for games rendering below display resolution.

Scope like #1509 (frame generation): opt-in, only when the frame carried usable motion data; falls back to the spatial scaler otherwise.