Add missing dataClasses for ProtocolMessage and PresenceMessage #521

• Currently, proto_message is shown as the hashmap/dictionary.
• Instead, it should be represented as a data class (POJO), so there will be few bugs while accessing properties from the class.
• Avoid the use of dict wherever possible and use data classes (POJOs) instead going forward.
• Remove dict antipattern from the code.
• Link to the internal discussion https://ably-real-time.slack.com/archives/CURL4U2FP/p1692608584322259?thread_ts=1692606259.572759&cid=CURL4U2FP

┆Issue is synchronized with this Jira Task by Unito