fix(win/video): don't offload chroma subsampling math to texture sampler when downscaling (#3014)

* Don't use sampler math for chroma if downscaling

* Correct portrait rotation offsets

src_assets/windows/assets/shaders/directx/cursor_vs.hlsl

@@ -6,5 +6,5 @@ cbuffer rotate_texture_steps_cbuffer : register(b2) {
 
 vertex_t main_vs(uint vertex_id : SV_VertexID)
 {
-    return generate_fullscreen_triangle_vertex(vertex_id, rotate_texture_steps);
+    return generate_fullscreen_triangle_vertex(vertex_id, float2(0, 0), rotate_texture_steps);
 }