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>

test/reload_test.go

@@ -181,7 +181,7 @@ func TestReloadSeveralTimeMetrics(t *testing.T) {
 		t.Errorf("Prometheus is not listening : %s", err)
 	}
 	reloadCount := 2
-	for i := 0; i < reloadCount; i++ {
+	for i := range reloadCount {
 		serverReload, err := serverWithMetrics.Restart(
 			NewInput(corefileWithMetrics),
 		)
@@ -305,7 +305,7 @@ func TestMetricsAvailableAfterReloadAndFailedReload(t *testing.T) {
 		t.Errorf("Could not scrap one of expected stats : %s", err)
 	}
 
-	for i := 0; i < 2; i++ {
+	for range 2 {
 		// now provide a failed reload
 		invInst, err := inst.Restart(
 			NewInput(invalidCorefileWithMetrics),