refactor: merge FH4+FH5 into 'forza_horizon', add separate FH6 game plugin

dashboards/forza_composite/manifest.json

@@ -5,7 +5,7 @@
     "description": "Forza 系列专属复合仪表：转速弧+档位大字+时速+油门刹车行程+油量水温",
     "author": "Yei.J. (AskaEth)",
     "version": "1.0.0",
-    "supported_games": "forza_horizon_5,forza_horizon_4,forza_motorsport",
+    "supported_games": "forza_horizon,forza_horizon_6,forza_motorsport",
     "config": {
         "icon": "🎮",
         "aspect_ratio": "16:9",