Fix HITMAN 3 boot, layered presentation, and socket imports (#851)

* videoout: synchronize layered flips with premultiplied composition

* shader: support unsigned FFBH subword sources

* shader: apply cube-face result scaling

* shader: prune buffer reads proven out of bounds

* net: implement send and receive exports with shared socket handling

---------

Co-authored-by: nmzik <Nmzik@mail.ru>

src/graphics/host_gpu/shaders/gpu_video_out_overlay.frag

@@ -0,0 +1,15 @@
+#version 450
+
+layout(location = 0) in vec2 uv;
+layout(location = 0) out vec4 color;
+layout(binding = 0) uniform sampler2D source;
+layout(push_constant) uniform AlphaControl {
+	uint premultiplied;
+};
+
+void main() {
+	color = texture(source, uv);
+	if (premultiplied == 0u) {
+		color.rgb *= color.a;
+	}
+}