[xPaw]

Fixes #1656.

• WebSocketContext.Dispose no longer runs a close handshake. RunSynchronously on CloseAsync threw whenever the socket was open, so Disconnected was never raised and CMClient.IsConnected stayed true.
• A stale context can no longer clear the current one, and a failed Send only disconnects the context it was sent on.
• Handler exceptions no longer kill the read loop: a throwing Connected handler disconnects, a throwing NetMsgReceived handler is logged, as in TcpConnection.
• Connect no longer throws when the handshake fails synchronously.
• Adds in-memory WebSocket tests for WebSocketConnection and SteamClient.

[JustArchi]

LGTM