all: use Go 1.22 range-over-int

Updates #11058

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

util/cstruct/cstruct_test.go

@@ -78,7 +78,7 @@ func TestDecoder(t *testing.T) {
 		dec := func(n int) *Decoder {
 			// Make a buffer of the exact size that consists of 0xff bytes
 			buf := make([]byte, n)
-			for i := 0; i < n; i++ {
+			for i := range n {
 				buf[i] = 0xff
 			}
 
@@ -108,7 +108,7 @@ func TestDecoder(t *testing.T) {
 		dec := func(n int) *Decoder {
 			// Make a buffer that's too small and contains arbitrary bytes
 			buf := make([]byte, n-1)
-			for i := 0; i < n-1; i++ {
+			for i := range n - 1 {
 				buf[i] = 0xAD
 			}