[SPARK-53233][SQL][FOLLOWUP] Add compatibility class/object for org.apache.spark.sql.execution.streaming

### What changes were proposed in this pull request?

This is a followup of #51959 . Although internal APIs are allowed to be changed, it's still better to keep compatibility if possible to avoid breaking existing Spark plugins.

This PR brings back `HDFSMetadataLog` and `SerializedOffset` to the original package, to avoid breaking the pulsar data source: https://github.com/streamnative/pulsar-spark/blob/master/src/main/scala/org/apache/spark/sql/pulsar/PulsarSources.scala#L27

### Why are the changes needed?

Avoid breaking Spark plugins

### Does this PR introduce _any_ user-facing change?

No

### How was this patch tested?

manual test

### Was this patch authored or co-authored using generative AI tooling?

no

Closes #52387 from cloud-fan/compat.

Lead-authored-by: Wenchen Fan <[email protected]>
Co-authored-by: Wenchen Fan <[email protected]>
Signed-off-by: Wenchen Fan <[email protected]>

Author: cloud-fan

sql/core/src/main/scala/org/apache/spark/sql/execution/streaming/legacy.scala

@@ -0,0 +1,33 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.execution.streaming
+
+import scala.reflect.ClassTag
+
+import org.apache.spark.sql.SparkSession
+import org.apache.spark.sql.execution.streaming.checkpointing.{HDFSMetadataLog => ActualHDFSMetadataLog}
+import org.apache.spark.sql.execution.streaming.runtime.{SerializedOffset => ActualSerializedOffset}
+
+@deprecated("use org.apache.spark.sql.execution.streaming.checkpointing.HDFSMetadataLog")
+class HDFSMetadataLog[T <: AnyRef: ClassTag](sparkSession: SparkSession, path: String)
+  extends ActualHDFSMetadataLog[T](sparkSession, path)
+
+@deprecated("use org.apache.spark.sql.execution.streaming.runtime.SerializedOffset")
+object SerializedOffset {
+  def apply(offset: String): ActualSerializedOffset = ActualSerializedOffset(offset)
+}