Add lifecycle callbacks for when push connection reconnects to new server

It is desirable for me to know when my clients' push connection reconnects but to a different server as using shared sessions the UI doesn't always re-render correctly thus we want to reload the page when this occurs. A standard way to do this is highly desirable. Right now, I am determining this by checking the clientId attribute of the JSON data coming from the server in a custom MessageHandler as the clientId resets when connecting to a new server. This seems error prone and is less than ideal.

Start by tracing the push connection lifecycle and the MessageHandler/clientId workaround described in the issue. Determine where a public lifecycle callback could distinguish reconnection to a different server, and verify that consumers can use it to trigger a page reload without inspecting JSON data.