We need to capture some tailnet-related information for some Docker
features we're building. This exposes the tailnet name and MagicDNS
information via `tailscale status --json`.
Fixestailscale/corp#3670
Signed-off-by: Ross Zurowski <ross@rosszurowski.com>
We're beginning to reference DERP region names in the admin UI, so it's
best to consolidate this information in our DERP map.
Signed-off-by: Ross Zurowski <ross@rosszurowski.com>