Problems with the implementation of DiscordWebsocketClient

[Ayplow]

• If DiscordWebsocketClient#close is called while DiscordWebsocketClient#_handle_closure is waiting to restart the connection, it will error due to the absence of _con. The connection will also still restart once the delay is up
• If bots stays online for too long, _connect and _handle_closure will eventually cause a RecursionError
• get_message sets up a race condition with the closure of the websocket that means the last time it is awaited before the connection is closed will never resume, preventing the client from ever finishing up.
  • A solution I tried for this was adding self._con._event_queue.put(False) to the close method. This technically works, but is clearly not ideal
• The heartbeat and restart tasks are not closed with the connection

Side note: DiscordWebsocketClient#_running is synonymous with _con at the moment, it can probably just be removed