all: use Go 1.22 range-over-int

Updates #11058

Change-Id: I35e7ef9b90e83cac04ca93fd964ad00ed5b48430
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

control/controlclient/controlclient_test.go

@@ -9,7 +9,7 @@ import (
 )
 
 func fieldsOf(t reflect.Type) (fields []string) {
-	for i := 0; i < t.NumField(); i++ {
+	for i := range t.NumField() {
 		if name := t.Field(i).Name; name != "_" {
 			fields = append(fields, name)
 		}

control/controlclient/map.go

@@ -563,7 +563,7 @@ var nodeFields = sync.OnceValue(getNodeFields)
 func getNodeFields() []string {
 	rt := reflect.TypeFor[tailcfg.Node]()
 	ret := make([]string, rt.NumField())
-	for i := 0; i < rt.NumField(); i++ {
+	for i := range rt.NumField() {
 		ret[i] = rt.Field(i).Name
 	}
 	return ret

control/controlclient/map_test.go

@@ -1019,7 +1019,7 @@ func BenchmarkMapSessionDelta(b *testing.B) {
 					Name: "foo.bar.ts.net.",
 				},
 			}
-			for i := 0; i < size; i++ {
+			for i := range size {
 				res.Peers = append(res.Peers, &tailcfg.Node{
 					ID:         tailcfg.NodeID(i + 2),
 					Name:       fmt.Sprintf("peer%d.bar.ts.net.", i),
@@ -1046,7 +1046,7 @@ func BenchmarkMapSessionDelta(b *testing.B) {
 
 			// Now for the core of the benchmark loop, just toggle
 			// a single node's online status.
-			for i := 0; i < b.N; i++ {
+			for i := range b.N {
 				if err := ms.HandleNonKeepAliveMapResponse(ctx, &tailcfg.MapResponse{
 					OnlineChange: map[tailcfg.NodeID]bool{
 						2: i%2 == 0,