Code refactoring

- Code refactoring
- Fix a bug that the other player will not become the host of the room at once, when the player disconnect in link play.

> Maybe add many unknown bugs. XD
> The song database `arcsong.db` will not used in the future. You can use a tool in `tool` folder to import old data.

latest version/core/system.py

@@ -0,0 +1,19 @@
+from time import time
+
+from .constant import Constant
+
+
+class GameInfo:
+    def __init__(self):
+        pass
+
+    def to_dict(self) -> dict:
+        return {
+            "max_stamina": Constant.MAX_STAMINA,
+            "stamina_recover_tick": Constant.STAMINA_RECOVER_TICK,
+            "core_exp": Constant.CORE_EXP,
+            "curr_ts": int(time()*1000),
+            "level_steps": [{'level': i, 'level_exp': Constant.LEVEL_STEPS[i]} for i in Constant.LEVEL_STEPS],
+            "world_ranking_enabled": True,
+            "is_byd_chapter_unlocked": True
+        }