[chore][internal/docker] Enable goleak check (#32046)

**Description:** 
This enables `goleak` to help ensure no goroutines are being leaked in
the `internal/docker` package. This is a test only change, an existing
test was leaking a goroutine because it wasn't cancelling a context
properly.

**Link to tracking Issue:** #30438 

**Testing:**
Existing tests are passing, as well as added `goleak` check.

internal/docker/docker_test.go

@@ -230,7 +230,9 @@ func TestEventLoopHandlesError(t *testing.T) {
 	assert.NotNil(t, cli)
 	assert.NoError(t, err)
 
-	go cli.ContainerEventLoop(context.Background())
+	ctx, cancel := context.WithCancel(context.Background())
+	go cli.ContainerEventLoop(ctx)
+	defer cancel()
 
 	assert.Eventually(t, func() bool {
 		for _, l := range logs.All() {

internal/docker/go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/docker/docker v25.0.5+incompatible
 	github.com/gobwas/glob v0.2.3
 	github.com/stretchr/testify v1.9.0
+	go.uber.org/goleak v1.3.0
 	go.uber.org/zap v1.27.0
 )
 

internal/docker/package_test.go

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