Added a single source of SDL object IDs

This ensures that we don't accidentally interpret an ID from one system as an ID in another system.
Audio device IDs are not covered here, since they have a unique numbering system.

src/sensor/android/SDL_androidsensor.c

@@ -152,7 +152,7 @@ static int SDL_ANDROID_SensorInit(void)
 
         for (i = 0; i < sensors_count; ++i) {
             SDL_sensors[i].asensor = sensors[i];
-            SDL_sensors[i].instance_id = SDL_GetNextSensorInstanceID();
+            SDL_sensors[i].instance_id = SDL_GetNextObjectID();
         }
         SDL_sensors_count = sensors_count;
     }