Make it easier to notify users that a new servicing release or newer GA release is available on non-preview builds. On preview builds, notify when new preview release is available.

We should probably push latest information to a well known Azure Blob during publishing time. On startup, have the check run on a separate thread to do the check and store some state (maybe just the latest version) on the system (probably a file). On next startup, if that file exists, compare versions and if running one is older, show the message.