create MemoryGameBoardStore Class and rework Building of Game Board Storage

server/game_board_stats/MemoryGameBoardStore.py

@@ -0,0 +1,17 @@
+from server.GameBoard import GameBoard
+
+class MemoryGameBoardStore:
+  def __init__(self, **kwargs):
+    self._state:dict[str, object] = {}
+
+  async def save(self, game_id:str, game_board:GameBoard) -> None:
+    self._state[game_id] = game_board
+
+  async def load(self, game_id:str):
+    return self._state.get(game_id)
+
+  async def delete(self, game_id:str) -> None:
+    self._state.pop(game_id, None)
+
+  async def close(self) -> None:
+    return None