net/netmon: unexport GetState

Baby step towards #15408.

Updates #15408

Change-Id: I11fca6e677af2ad2f065d83aa0d83550143bff29
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

net/netmon/interfaces_test.go

@@ -13,7 +13,7 @@ import (
 )
 
 func TestGetState(t *testing.T) {
-	st, err := GetState()
+	st, err := getState()
 	if err != nil {
 		t.Fatal(err)
 	}

net/netmon/netmon.go

@@ -161,7 +161,7 @@ func (m *Monitor) InterfaceState() *State {
 }
 
 func (m *Monitor) interfaceStateUncached() (*State, error) {
-	return GetState()
+	return getState()
 }
 
 // SetTailscaleInterfaceName sets the name of the Tailscale interface. For

net/netmon/state.go

@@ -466,7 +466,7 @@ var getPAC func() string
 // It does not set the returned State.IsExpensive. The caller can populate that.
 //
 // Deprecated: use netmon.Monitor.InterfaceState instead.
-func GetState() (*State, error) {
+func getState() (*State, error) {
 	s := &State{
 		InterfaceIPs: make(map[string][]netip.Prefix),
 		Interface:    make(map[string]Interface),