[SPARK-52513] Add a streaming word count example with rolling event logs

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

This PR aims to add a streaming word count example, `org.apache.spark.examples.streaming.HdfsWordCount`.

In addition, this example will show a event log rolling feature which is enabled by default in Apache Spark 4.0.0.

```yaml
spark.eventLog.enabled: "true"
spark.eventLog.dir: "s3a://spark-events/"
spark.eventLog.rolling.maxFileSize: "10m"
```

```
$ aws s3 --profile localstack ls s3://spark-events/ --recursive
2025-06-17 09:43:55          0 eventlog_v2_stream-word-count-0/
2025-06-17 09:43:55          0 eventlog_v2_stream-word-count-0/appstatus_stream-word-count-0.inprogress
2025-06-17 09:52:02    1957278 eventlog_v2_stream-word-count-0/events_1_stream-word-count-0.zstd
```

### Why are the changes needed?

To show a streaming example with event log.

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

No behavior change because this is an example.

### How was this patch tested?

Manual tests.

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

No.

Closes apache#251 from dongjoon-hyun/SPARK-52513.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

examples/localstack.yml

@@ -39,6 +39,7 @@ spec:
           - -c
           - >
             awslocal s3 mb s3://spark-events;
+            awslocal s3 mb s3://ingest;
             awslocal s3 mb s3://data;
             awslocal s3 cp /opt/code/localstack/Makefile s3://data/
 ---

examples/stream-word-count.yaml

@@ -0,0 +1,40 @@
+# 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.
+apiVersion: spark.apache.org/v1beta1
+kind: SparkApplication
+metadata:
+  name: stream-word-count
+spec:
+  mainClass: "org.apache.spark.examples.streaming.HdfsWordCount"
+  jars: "local:///opt/spark/examples/jars/spark-examples.jar"
+  driverArgs: [ "s3a://ingest" ]
+  sparkConf:
+    spark.jars.packages: "org.apache.hadoop:hadoop-aws:3.4.1"
+    spark.jars.ivy: "/tmp/.ivy2.5.2"
+    spark.dynamicAllocation.enabled: "true"
+    spark.dynamicAllocation.shuffleTracking.enabled: "true"
+    spark.dynamicAllocation.maxExecutors: "3"
+    spark.kubernetes.authenticate.driver.serviceAccountName: "spark"
+    spark.kubernetes.container.image: "apache/spark:4.0.0-java21-scala"
+    spark.log.level: "WARN"
+    spark.eventLog.enabled: "true"
+    spark.eventLog.dir: "s3a://spark-events/"
+    spark.eventLog.rolling.maxFileSize: "10m"
+    spark.hadoop.fs.s3a.endpoint: "http://localstack:4566"
+    spark.hadoop.fs.s3a.path.style.access: "true"
+    spark.hadoop.fs.s3a.access.key: "test"
+    spark.hadoop.fs.s3a.secret.key: "test"
+  runtimeVersions:
+    sparkVersion: "4.0.0"