Part of #1153, #1154. Fixes #1224. Signed-off-by: David Anderson <danderson@tailscale.com>
And move a couple other types down into leafier packages. Now cmd/tailscale doesn't bring in netlink, magicsock, wgengine, etc. Fixes #1181 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>