Cleanup shader generation code (#10663)

Shader generation is a mess. This commit cleans some parts up, including dropping remains of HLSL support which was never actually implemented.

src/client/game.cpp

@@ -475,12 +475,8 @@ class GameGlobalShaderConstantSetter : public IShaderConstantSetter
 		g_settings->deregisterChangedCallback("enable_fog", settingsCallback, this);
 	}
 
-	virtual void onSetConstants(video::IMaterialRendererServices *services,
-			bool is_highlevel)
+	void onSetConstants(video::IMaterialRendererServices *services) override
 	{
-		if (!is_highlevel)
-			return;
-
 		// Background color
 		video::SColor bgcolor = m_sky->getBgColor();
 		video::SColorf bgcolorf(bgcolor);