lint: enable intrange linter (#7331)

Enable intrange linter to enforce modern Go range syntax over
traditional for loops, by converting:

for i := 0; i < n; i++

to:

for i := range n

Adding type conversions where needed for compatibility
with existing uint64 parameters.

Signed-off-by: Ville Vesilehto <ville@vesilehto.fi>

plugin/etcd/msg/service.go

@@ -164,7 +164,7 @@ func split255(s string) []string {
 // targetStrip strips "targetstrip" labels from the left side of the fully qualified name.
 func targetStrip(name string, targetStrip int) string {
 	offset, end := 0, false
-	for i := 0; i < targetStrip; i++ {
+	for range targetStrip {
 		offset, end = dns.NextLabel(name, offset)
 	}
 	if end {