cmd/tailscale: change formatting of "tailscale status"

* show DNS name over hostname, removing domain's common MagicDNS suffix.
  only show hostname if there's no DNS name.
  but still show shared devices' MagicDNS FQDN.

* remove nerdy low-level details by default: endpoints, DERP relay,
  public key.  They're available in JSON mode still for those who need
  them.

* only show endpoint or DERP relay when it's active with the goal of
  making debugging easier. (so it's easier for users to understand
  what's happening) The asterisks are gone.

* remove Tx/Rx numbers by default for idle peers; only show them when
  there's traffic.

* include peers' owner login names

* add CLI option to not show peers (matching --self=true, --peers= also
  defaults to true)

* sort by DNS/host name, not public key

* reorder columns

wgengine/magicsock/magicsock.go

@@ -2710,11 +2710,14 @@ func (c *Conn) UpdateStatus(sb *ipnstate.StatusBuilder) {
 	ss := &ipnstate.PeerStatus{
 		PublicKey: c.privateKey.Public(),
 		Addrs:     c.lastEndpoints,
+		OS:        version.OS(),
 	}
 	if c.netMap != nil {
 		ss.HostName = c.netMap.Hostinfo.Hostname
-		ss.OS = version.OS()
 		ss.DNSName = c.netMap.Name
+		ss.UserID = c.netMap.User
+	} else {
+		ss.HostName, _ = os.Hostname()
 	}
 	if c.derpMap != nil {
 		derpRegion, ok := c.derpMap.Regions[c.myDerp]