[chore][pkg/stanza/operator/helper] Enable goleak check (open-telemet…

…ry#31092)

This enables `goleak` in the `pkg/stanza/operator/helper` package to
help ensure no goroutines are leaking. This is a test only change, some
tests were simply missing `Stop` calls.

**Link to tracking Issue:** open-telemetry#30438

pkg/stanza/operator/helper/ip_resolver_test.go

@@ -18,6 +18,7 @@ func TestIPResolverCacheLookup(t *testing.T) {
 	}
 
 	require.Equal(t, "definitely invalid hostname", resolver.GetHostFromIP("127.0.0.1"))
+	resolver.Stop()
 }
 
 func TestIPResolverCacheInvalidation(t *testing.T) {
@@ -45,6 +46,7 @@ func TestIPResolver100Hits(t *testing.T) {
 	for i := 0; i < 100; i++ {
 		require.Equal(t, "definitely invalid hostname", resolver.GetHostFromIP("127.0.0.1"))
 	}
+	resolver.Stop()
 }
 
 func TestIPResolverWithMultipleStops(_ *testing.T) {

pkg/stanza/operator/helper/package_test.go

@@ -0,0 +1,14 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package helper
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m)
+}