Chart Seek Bugfix (#545)

* fix lag spike when starting playback from middle of chart

further optimization to GameManager which considerably reduces garbage generation

* let dsp offset be calculated on playback start if needed

Assets/Scripts/Minigames.cs

@@ -501,6 +501,16 @@ namespace HeavenStudio
             }
         }
 
+        public class InputAction
+        {
+            public string name;
+            public List<InputActionEntry> mappings;
+        }
+
+        public class InputActionEntry
+        {
+        }
+
         public delegate void EventCallback();
         public delegate void ParamChangeCallback(string paramName, object paramValue, RiqEntity entity);