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_test.go

@@ -8,7 +8,7 @@ func TestSplit255(t *testing.T) {
 		t.Errorf("Failure to split abc")
 	}
 	s := ""
-	for i := 0; i < 255; i++ {
+	for range 255 {
 		s += "a"
 	}
 	xs = split255(s)
@@ -20,7 +20,7 @@ func TestSplit255(t *testing.T) {
 	if len(xs) != 2 || xs[1] != "b" {
 		t.Errorf("Failure to split 256 char long string: %d", len(xs))
 	}
-	for i := 0; i < 255; i++ {
+	for range 255 {
 		s += "a"
 	}
 	xs = split255(s)