This sets up Logger to handle statistics at the magicsock layer,
where we can correlate traffic between a particular tailscale IP address
and any number of physical endpoints used to contact the node
that hosts that tailscale address.
We also export Message and TupleCounts to better document the JSON format
that is being sent to the logging infrastructure.
This commit does NOT yet enable the actual logging of magicsock statistics.
That will be a future commit.
Signed-off-by: Joe Tsai <joetsai@digital-static.net>
a1a43ed266