Enable stateful reconnects (#35658)

RFC

- Requires https://github.com/ppy/osu-server-spectator/pull/366 to
actually function.

Resolves https://github.com/ppy/osu/issues/35580
Resolves https://github.com/ppy/osu-server-spectator/issues/193
Resolves https://github.com/ppy/osu/issues/35586
Resolves https://github.com/ppy/osu-server-spectator/issues/362
Resolves https://github.com/ppy/osu/issues/37353

## Outline

This enables stateful reconnect for spectator-server endpoints, allowing
ConnectionIds to be preserved for a short period and messages to be
replayed on reconnect.

In practice, this means short disconnects (<30s) should no longer:
- Drop replays
- Kick you out of multiplayer rooms
- Trigger "user has come online" re-alerts.

The following video demonstrates two of the above:


https://github.com/user-attachments/assets/b9781f31-a8a1-410e-b0ac-65d3374a33d6

Stateful reconnect appears to kick in as long as the socket doesn't get
disconnected, _not_ on subsequent re-connections. We have the timeout
period set to SignalR's default of 30sec.

I've been using the following to simulate a total link loss:

```sh
#!/bin/bash

DELAY=${1:-1}

echo "Conditioning for $DELAY seconds..."

sudo ip link set lo down
sudo ss -K dst 127.0.0.2 > /dev/null
sleep $DELAY
sudo ip link set lo up
```

osu.Game/Online/HubClientConnector.cs

@@ -64,6 +64,8 @@ namespace osu.Game.Online
                     options.Headers.Add(CLIENT_SESSION_ID_HEADER, API.SessionIdentifier.ToString());
                 });
 
+            builder.WithStatefulReconnect();
+
             builder.AddMessagePackProtocol(options =>
             {
                 options.SerializerOptions = SignalRUnionWorkaroundResolver.OPTIONS;