HostLink session state and frame routing

The code does not have a HostlinkSession class. A session is expressed byLinkState、Status、SessionRuntime and a set of explicit functions.

Separation of duties

• Transport transports bytes.
• SessionRuntime saves the link, sequence number, deadline and status/GPS throttling.
• Frame router produces type decisions.
• service/config/event/app-data codecs translation payload.

Drill down: LinkState and handshake life cycle