s3: optimize DELETE by skipping lock check for buckets without Object Lock (#7642)

This optimization avoids an expensive filer gRPC call for every DELETE
operation on buckets that don't have Object Lock enabled.

Before this change, enforceObjectLockProtections() would always call
getObjectEntry() to fetch object metadata to check for retention/legal
hold, even for buckets that never had Object Lock configured.

Changes:
1. Add early return in enforceObjectLockProtections() if bucket has no
   Object Lock config or bucket doesn't exist
2. Add isObjectLockEnabled() helper function to check if a bucket has
   Object Lock configured
3. Fix validateObjectLockHeaders() to check ObjectLockConfig instead of
   just versioningEnabled - this ensures object-lock headers are properly
   rejected on buckets without Object Lock enabled, which aligns with
   AWS S3 semantics
4. Make bucket creation with Object Lock atomic - set Object Lock config
   in the same CreateEntry call as bucket creation, preventing race
   conditions where bucket exists without Object Lock enabled
5. Properly handle Object Lock setup failures during bucket creation -
   if StoreObjectLockConfigurationInExtended fails, roll back the bucket
   creation and return an error instead of leaving a bucket without
   the requested Object Lock configuration

This significantly improves DELETE latency for non-Object-Lock buckets,
which is the common case (lockCheck time reduced from 1-10ms to ~1µs).

test/s3/retention/s3_object_lock_headers_test.go

@@ -236,7 +236,7 @@ func TestObjectLockHeadersNonVersionedBucket(t *testing.T) {
 	bucketName := getNewBucketName()
 
 	// Create regular bucket without object lock/versioning
-	createBucket(t, client, bucketName)
+	createBucketWithoutObjectLock(t, client, bucketName)
 	defer deleteBucket(t, client, bucketName)
 
 	key := "test-non-versioned"

test/s3/retention/s3_retention_test.go

@@ -69,8 +69,19 @@ func getNewBucketName() string {
 	return fmt.Sprintf("%s%d", defaultConfig.BucketPrefix, timestamp)
 }
 
-// createBucket creates a new bucket for testing
+// createBucket creates a new bucket for testing with Object Lock enabled
+// Object Lock is required for retention and legal hold functionality per AWS S3 specification
 func createBucket(t *testing.T, client *s3.Client, bucketName string) {
+	_, err := client.CreateBucket(context.TODO(), &s3.CreateBucketInput{
+		Bucket:                     aws.String(bucketName),
+		ObjectLockEnabledForBucket: aws.Bool(true),
+	})
+	require.NoError(t, err)
+}
+
+// createBucketWithoutObjectLock creates a new bucket without Object Lock enabled
+// Use this only for tests that specifically need to verify non-Object-Lock bucket behavior
+func createBucketWithoutObjectLock(t *testing.T, client *s3.Client, bucketName string) {
 	_, err := client.CreateBucket(context.TODO(), &s3.CreateBucketInput{
 		Bucket: aws.String(bucketName),
 	})