ViaVersion

1735812 Fix: delay chat acknowledgements instead of spoofing (#3997)

An easy reproduction case is to mute a player using the Social Interactions screen, let them chat, and then send a message. As ViaVersion produces its own acknowledgements, this now does not match with what the client produced and signed its messages with - so the signature will fail verification.

As an alternative, we always pass through the same acknowledgement bit set - and for 'spoofed' messages, we reuse the last one that we received. In the case of the chat ack packet with just an offset, we need to hold back the window by at least 20 messages to ensure we don't start making claims about whether the client saw a message that ViaVersion cannot yet make a judgement on.