all: use Go 1.22 range-over-int

Updates #11058

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

cmd/tailscale/cli/cli_test.go

@@ -831,7 +831,7 @@ func TestPrefFlagMapping(t *testing.T) {
 	}
 
 	prefType := reflect.TypeFor[ipn.Prefs]()
-	for i := 0; i < prefType.NumField(); i++ {
+	for i := range prefType.NumField() {
 		prefName := prefType.Field(i).Name
 		if prefHasFlag[prefName] {
 			continue

cmd/tailscale/cli/network-lock.go

@@ -148,7 +148,7 @@ func runNetworkLockInit(ctx context.Context, args []string) error {
 	}
 
 	fmt.Printf("%d disablement secrets have been generated and are printed below. Take note of them now, they WILL NOT be shown again.\n", nlInitArgs.numDisablements)
-	for i := 0; i < nlInitArgs.numDisablements; i++ {
+	for range nlInitArgs.numDisablements {
 		var secret [32]byte
 		if _, err := rand.Read(secret[:]); err != nil {
 			return err

cmd/tailscale/cli/serve_legacy.go

@@ -387,7 +387,7 @@ func isProxyTarget(source string) bool {
 // allNumeric reports whether s only comprises of digits
 // and has at least one digit.
 func allNumeric(s string) bool {
-	for i := 0; i < len(s); i++ {
+	for i := range len(s) {
 		if s[i] < '0' || s[i] > '9' {
 			return false
 		}