Instead of opening tuntox buffer, use messages

The Tuntox Proxy buffer is mostly useful to those who know about the low-level operation of crdt.el. So, instead of always opening that process buffer when it is created, leave the process buffer in the background and use process filters to post more user-friendly notifications about tuntox connection status to Messages.

I'm not that familiar with process filters, but I saw that overriding the default filter causes the buffer to no longer get updated by default, so I copied the way the crdt-connect tuntox filter writes to the process buffer into crdt-new-session as well.

Co-authored-by: @artenator