correcting benchmark data payload format and parsing messages

[prog-supdex]

What changed

• Removed JSON.stringify when sending the payload in the data field, now sending the raw object
• Enhanced the pusher:connection_established and client-broadcast handlers to parse msg.data correctly, whether it’s a string or an object
• Added checks for ws.readyState === WS_OPEN before every ws.send in pusher:ping event to avoid errors when the socket is closed

Why

Prior payload serialization was causing server errors ("data field must be an array") and complicated client-side parsing. These updates ensure full compatibility with Reverb, AnyCable, and Soketi, allowing reliable collection of latency and throughput metrics without errors.