control/controlclient: store netinfo and hostinfo separately

Currently, when SetNetInfo is called it sets the value on
hostinfo.NetInfo. However, when SetHostInfo is called it overwrites the
hostinfo field which may mean it also clears out the NetInfo it had just
received.
This commit stores NetInfo separately and combines it into Hostinfo as
needed so that control is always notified of the latest values.

Also, remove unused copies of Hostinfo from ipn.Status and
controlclient.Auto.

Updates #tailscale/corp#4824 (maybe fixes)

Signed-off-by: Maisem Ali <maisem@tailscale.com>

ipn/ipnlocal/local.go

@@ -935,8 +935,7 @@ func (b *LocalBackend) Start(opts ipn.Options) error {
 	httpTestClient := b.httpTestClient
 
 	if b.hostinfo != nil {
-		hostinfo.Services = b.hostinfo.Services // keep any previous session and netinfo
-		hostinfo.NetInfo = b.hostinfo.NetInfo
+		hostinfo.Services = b.hostinfo.Services // keep any previous services
 	}
 	b.hostinfo = hostinfo
 	b.state = ipn.NoState
@@ -2870,9 +2869,6 @@ func (b *LocalBackend) assertClientLocked() {
 func (b *LocalBackend) setNetInfo(ni *tailcfg.NetInfo) {
 	b.mu.Lock()
 	cc := b.cc
-	if b.hostinfo != nil {
-		b.hostinfo.NetInfo = ni.Clone()
-	}
 	b.mu.Unlock()
 
 	if cc == nil {