[SPARK-54147][SQL] Set OMP_NUM_THREADS to spark.task.cpus by default in BaseScriptTransformationExec

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

Set OMP_NUM_THREADS to spark.task.cpus by default in BaseScriptTransformationExec

### Why are the changes needed?

When we use the TRANSFORM function to invoke a Python script，the Python script uses packages such as PyTorch or NumPy. Since these libraries, by default, start a number of intra-op threads equal to the number of available CPU cores on the node, this can lead to CPU overload.
```
ADD ARCHIVE s3://example-bucket/udf/emotion/emotion_predict.zip;
ADD ARCHIVE s3://example-bucket/udf/emotion/python_env.zip;

INSERT OVERWRITE TABLE demo_db.text_emotion_result PARTITION (dt = 'XXX')
SELECT
    TRANSFORM(
        id,
        title,
        content
    )
    USING './python_env.zip/python_env/bin/python emotion_predict.zip/emotion_predict/predict.py'
    AS (id, title, content, emotion_label, emotion_score)
FROM (
    SELECT /*+ REPARTITION(1000) */
        id, title, content
    FROM demo_db.text_input_data
    WHERE dt = 'XXX'
) src;
```

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

No.

### How was this patch tested?

Manually.

Closes #52850 from TongWei1105/SPARK-54147.

Authored-by: TongWei1105 <[email protected]>
Signed-off-by: Yuming Wang <[email protected]>

Author: TongWei1105

sql/core/src/main/scala/org/apache/spark/sql/execution/BaseScriptTransformationExec.scala

@@ -84,6 +84,10 @@ trait BaseScriptTransformationExec extends UnaryExecNode {
     val path = System.getenv("PATH") + File.pathSeparator +
       SparkFiles.getRootDirectory()
     builder.environment().put("PATH", path)
+    // if OMP_NUM_THREADS is not explicitly set, override it with the value of "spark.task.cpus"
+    if (System.getenv("OMP_NUM_THREADS") == null) {
+      builder.environment().put("OMP_NUM_THREADS", conf.getConfString("spark.task.cpus", "1"))
+    }
 
     val proc = builder.start()
     val inputStream = proc.getInputStream