all: use Go 1.22 range-over-int

Updates #11058

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

metrics/metrics_test.go

@@ -41,7 +41,7 @@ func TestCurrentFileDescriptors(t *testing.T) {
 
 	// Open some FDs.
 	const extra = 10
-	for i := 0; i < extra; i++ {
+	for i := range extra {
 		f, err := os.Open("/proc/self/stat")
 		if err != nil {
 			t.Fatal(err)
@@ -58,7 +58,7 @@ func TestCurrentFileDescriptors(t *testing.T) {
 
 func BenchmarkCurrentFileDescriptors(b *testing.B) {
 	b.ReportAllocs()
-	for i := 0; i < b.N; i++ {
+	for range b.N {
 		_ = CurrentFDs()
 	}
 }

metrics/multilabelmap.go

@@ -61,7 +61,7 @@ func labelString(k any) string {
 	var sb strings.Builder
 	sb.WriteString("{")
 
-	for i := 0; i < t.NumField(); i++ {
+	for i := range t.NumField() {
 		if i > 0 {
 			sb.WriteString(",")
 		}